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The article discusses an optimization strategy designed to improve the International Seismological Centre (ISC) earthquake focal mechanism computations. The authors detail how this can minimize an objective misfit function before describing how the optimized automatic picker to increase the number of first motion auto-picked polarities.

Rarely does research in the history and philosophy of science lead to new empirical results, but that is exactly what has happened in one of the essays of this special issue: Rang and Grebe-Ellis have developed new experimental techniques to perform measurements Goethe proposed 217 years ago. These measurements fit neatly with Goethe’s idea of polarity—his complementary spectrum is not only an optical, but also a thermodynamical counterpart of Newton’s spectrum. I use the new measurements, firstly, to argue against the asymmetries between light and darkness posited by Lyre and Schreiber; and, secondly, to explicate the alternative theory (the heterogeneity of darkness) that Goethe had introduced to urge scientific pluralism. In my replies to exegetical criticism by Böhler, Hampe and Zemplén, I show that the main goal of Goethe’s Farbenlehre was indeed to expose symmetries between light and darkness. Furthermore, I argue that it is worthwhile to focus on the experiments, arguments and hypotheses of the Farbenlehre, and not merely on rhetorical, narrative or stylistical aspects, as Böhler and Hampe would have it. Goethe’s criticism of Newton is often dismissed, but it is in fact surprisingly relevant today. [ABSTRACT FROM AUTHOR]

Neuronal excitability is determined in a complex way by several interacting factors, such as membrane dynamics, fibre geometry, electrode configuration, myelin impedance, neuronal terminations[Formula: see text] This study aims to increase understanding in excitability, by investigating the impact of these factors on different models of myelinated and unmyelinated fibres (five well-known membrane models are combined with three electrostimulation models, that take into account the spatial structure of the neuron). Several excitability indices (rheobase, polarity ratio, bi/monophasic ratio, time constants[Formula: see text]) are calculated during extensive parameter sweeps, allowing us to obtain novel findings on how these factors interact, e.g. how the dependency of excitability indices on the fibre diameter and myelin impedance is influenced by the electrode location and membrane dynamics. It was found that excitability is profoundly impacted by the used membrane model and the location of the neuronal terminations. The approximation of infinite myelin impedance was investigated by two implementations of the spatially extended non-linear node model. The impact of this approximation on the time constant of strength-duration plots is significant, most importantly in the Frankenhaeuser-Huxley membrane model for large electrode-neuron separations. Finally, a multi-compartmental model for C-fibres is used to determine the impact of the absence of internodes on excitability. Graphical Abstract Electrostimulation models, obtained by combining five membrane models with three representations of the neuronal cable equation, are fed with electrode and stimulus input parameters. The dependency of neuronal excitability on the interaction of these input parameters is determined by deriving excitability indices from the spatiotemporal model response. The impact of the myelin impedance and the fibre diameter on neural excitability is also considered. [ABSTRACT FROM AUTHOR]

The Stokes axisymmetrical microstretch streaming flow problem past a stationary viscous droplet and as well as the related problem of a viscous streaming flow past a stationary microstretch fluid droplet are studied. The droplets are considered either perfect spherical or deformed spherical in shape. For these flows, the microstretch scalar function is uncoupled from the stream function and microrotation component function. As boundary conditions, continuity of velocity, continuity of shear stress, vanishing of microstretch and the spin-vorticity relation at the droplet surface are used. Analytical solutions are obtained in each case for the stream functions and microstretch scalar. The drag acting, in each case, on the fluid droplet is evaluated. Numerical results for the drag force coefficient versus the relative viscosity, micropolarity parameter and spin parameter (a non-dimensional scalar factor relating the microrotation and vorticity at the droplet surface) are presented both in tabular and graphical forms. The results for the drag coefficient are compared with the available solutions in the literature for the limiting cases. [ABSTRACT FROM AUTHOR]

Lightning is the main cause of transmission system outages, affecting reliability of power supply and resulting in economic losses. Shielding failure is an important issue in addressing the lightning performance of overhead transmission lines. In this paper an improved method based on the electro-geometric model is proposed to evaluate the shielding failure flashover rate (SFFOR) of transmission lines, considering the influences of landform, lightning polarity and stroke angle. In the improved method, the striking distances to phase conductors, shield wires and ground are properly differentiated by using recent equations developed to take into account other factors not only magnitude of lightning strokes. These factors include height of wires as well as lightning polarity. To reflect the effects of changes in terrain and height of wires on SFFOR, a method for identifying the topography and the relative position among the wires and ground is proposed. A 400-kV double-circuit transmission line section in complex terrain area was taken as example, and the results show that this method can reflect changes of the SFFOR along the span and can be useful to figure out which towers are easy to be struck by lightning along the entire transmission line. This research is helpful for the design and operation of overhead transmission lines. [ABSTRACT FROM AUTHOR]

An ICCD camera was used to study plasma glow at the stage of the streamer (ionization wave) formation in the tip-plane gap with a length of 3 mm filled with argon or nitrogen at a pressure of 12.5-400 kPa. Positive and negative nanosecond voltage pulses were applied across the gap. Images of streamer were obtained at different time at its propagation along the gap. A streak-camera equipped with a spectrometer was used to measure time evolution of the radiation intensity of nitrogen molecules at a wavelength of 337.1 nm in several regions along the gap at the negative polarity. Average streamer velocity (1.8 cm/ns) was estimated from experimental data at atmospheric pressure of nitrogen. Amplitude-time characteristics of voltage, discharge current and the current of runaway electron beam behind the aluminum-foil anode with a thickness of 10 μm were measured. Reasons for a diffuse discharge under the given experimental conditions were discussed. [ABSTRACT FROM AUTHOR]

Molecular descriptors are graph invariants representing the chemical structure in graph-theoretical terms. There is a wide range of such descriptors and the computation of these invariants for the various chemical frameworks is a current area of research. Among these the Wiener types of indices have passed through critical tests and emerged as a useful topological index in QSAR, predictive toxicology and computer-assisted drug discovery as a starting point to reduce a large data set of chemicals. However mathematical techniques to compute hyper-Wiener index continues to pose considerable challenges, as they involve long and complex manipulations. In the present study, we develop a new technique based on vertex cut methods to compute the hyper-Wiener indices of complex silicate and oxide frameworks of current interest for the first time and obtain the analytical expressions of Wiener polarity indices for these chemical frameworks based on vertex neighborhood. [ABSTRACT FROM AUTHOR]

The results of comparative analysis of the behavior of paleointensity and polarity (intervals between reversals) of the geomagnetic field for the last 167 Ma are presented. Similarities and differences in the behavior of these characteristics of the geomagnetic field are discussed. It is shown that bursts of paleointensity and long intervals between reversals occurred at high mean values of paleointensity in the Cretaceous and Paleogene. However, there are differences between the paleointensity behavior and the reversal regime: (1) the characteristic times of paleointensity variations are less than the characteristic times of the frequency of geomagnetic reversals, (2) the achievement of maximum values of paleointensity at the Cretaceous-Paleogene boundary and the termination of paleointensity bursts after the boundary of 45-40 Ma are not marked by explicit features in the geomagnetic polarity behavior. [ABSTRACT FROM AUTHOR]

The M flare that arises after magnetic field emersion in a small spot is analyzed. The disturbance, which propagated downwards and generated a source of acoustic waves (sunquake), was simultaneous with an outburst of hard X-radiation. The reasons of such sunquakes are discussed. Rearrangement of the magnetic configuration in the analyzed event is confirmed: field lines and strong currents at low altitudes above the polarity boundary line are transformed into the currents along the system of loops oriented at wide angles to the neutral line. This rearrangement occurred in the proximity of a small region (sigmoid) presumably identified by the location of the primary pulse energy release. In this case, there was no development of a high-energy sigmoid flare with the formation and ejection of large-scale magnetized ropes. Apparently, this was hindered by the nonstationarity of the phenomena at this activity center with a magnetic field of composite topology and multiple flare-generating centers. [ABSTRACT FROM AUTHOR]

The magnetic properties of the shadow of magnetic-related leading and trailing spots (those connected by forces lines of magnetic field, which are calculated from a field in potential approximation) are studied in this work. The correlations are established between individual characteristics of the field in the spot shadow and these characteristics from the shadow area S for spot pairs, for which the minimum angle between the measured vector of magnetic induction B in the shadow of the leading (L) spot and positive normal to the solar surface is lower than in the trailing (F) spot (αmin-L < αmin-F) and, vice versa, when αmin-L > αmin-F. It is shown that the αmin-L(SL), αmin-F(SF), Bmax-L(SL) and Bmax-F(SF) correlations are similar behaviorally and quantitatively for two groups of spots with different asymmetries of a magnetically connected field (Bmax-L, F is the maximum of magnetic induction in the shadow of leading and trailing spots). The correlation between the average angles within the spot shadow 〈αL, F〉 and the area of the spot shadow SL, F and between the average value of magnetic induction in the spot shadow 〈BL, F〉 differ in two cases. In most studied spot pairs, the leading spot is closer to the dividing line of polarity between the spots rather than the trailing one. [ABSTRACT FROM AUTHOR]

We study the relationship between polar field reversals and decayed active region magnetic flux. Photospheric active region flux is dispersed by differential rotation and turbulent diffusion, and is transported poleward by meridional flows and diffusion. We summarize the published evidence from observation and modeling of the influence of meridional flow variations and decaying active region flux's spatial distribution, such as the Joy's law tilt angle. Using NSO Kitt Peak synoptic magnetograms covering cycles 21-24, we investigate in detail the relationship between the transport of decayed active region flux to high latitudes and changes in the polar field strength, including reversals in the magnetic polarity at the poles. By means of stack plots of low- and high-latitude slices of the synoptic magnetograms, the dispersal of flux from low to high latitudes is tracked, and the timing of this dispersal is compared to the polar field changes. In the most abrupt cases of polar field reversal, a few activity complexes (systems of active regions) are identified as the main cause. The poleward transport of large quantities of decayed trailing-polarity flux from these complexes is found to correlate well in time with the abrupt polar field changes. In each case, significant latitudinal displacements were found between the positive and negative flux centroids of the complexes, consistent with Joy's law bipole tilt with trailing-polarity flux located poleward of leading-polarity flux. The activity complexes of the cycle 21 and 22 maxima were larger and longer-lived than those of the cycle 23 and 24 maxima, and the poleward surges were stronger and more unipolar and the polar field changes larger and faster. The cycle 21 and 22 polar reversals were dominated by only a few long-lived complexes whereas the cycle 23 and 24 reversals were the cumulative effects of more numerous, shorter-lived regions. We conclude that sizes and lifetimes of activity complexes are key to understanding the diversity of polar reversals. [ABSTRACT FROM AUTHOR]

In this paper, an ion source based on wire-to-plate corona is developed for Ion Mobility Spectrometer (IMS). The characteristics of the corona discharge and the ion current detected on Faraday plate are investigated under different electrode spacing and voltage. The effect of voltage polarity is also studied. The features of this new designed ion source are compared with that of point-to-plate corona. The results show that the present IMS prototype machine can provide a much larger value of ion current connected by Faraday plate than the point-to-plate corona and/or the traditional 63Ni source. The corona configuration can also act as a good electromagnetic shielding to defense the electromagnetic emission from the corona discharge. [ABSTRACT FROM AUTHOR]

Theoretical investigation is carried out for understanding the properties of nonlinear dust-acoustic (DA) waves in an unmagnetized dusty plasma whose constituents are massive, micron-sized, positive and negatively charged inertial dust grains along with q (nonextensive) distributed electrons and ions. The reductive perturbation method is employed in order to derive two types of nonlinear dynamical equations, namely, Burgers equation and modified Gardner equation (Gardner equation with dissipative term). They are also numerically analyzed to investigate the basic features (viz., polarity, amplitude, width, etc.) of shock waves and double layers. It has been observed that the effects of nonextensivity, opposite polarity charged dust grains, and different dusty plasma parameters have significantly modified the fundamental properties of shock waves and double layers. The results of this investigation may be used for researches of the nonlinear wave propagation in laboratory and space plasmas. [ABSTRACT FROM AUTHOR]

A rigorous theoretical investigation has been carried out on the propagation of nonplanar (cylindrical and spherical) dust-acoustic shock waves (DASHWs) in a collisionless four-component unmagnetized dusty plasma system containing massive, micron-sized, positively and negatively charged inertial dust grains along with q (nonextensive) distributed electrons and ions. The well-known reductive perturbation technique has been used to derive the modified Burgers equation (which describes the shock wave properties) and its numerical solution. It has been observed that the effects of charged dust grains of opposite polarity, nonextensivity of electrons and ions, and different dusty plasma parameters have significantly modified the fundamental properties (viz., polarity, amplitude, width, etc.) of the shock waves. The properties of DASHWs in nonplanar geometry are found to be significantly different from those in one-dimensional planar geometry. The findings of our results from this theoretical investigation may be useful in understanding the nonlinear features of localized electrostatic disturbances in both space and laboratory dusty plasmas. [ABSTRACT FROM AUTHOR]

The initiation of discharge by model hydrometeors between an artificial-thunderstorm cell (aerosol cloud) of negative or positive polarity and ground has been experimentally studied. It is established for the first time that the conditions of cloud-ground spark discharge initiation by hydrometeors, as well as the characteristics of discharge significantly depend on the polarity of charged cloud. The effect of hydrometeor arrays can be manifested by the cloud-ground lightning initiated in a thundercloud and used for developing scientific principles of artificial lightning discharge. [ABSTRACT FROM AUTHOR]

Effects of fluctuational dissipative perturbations on the Earth's polar motion due to random components of the centrifugal potential are studied using a numerical-analytical approach. A combined model for the polar fluctuations is used to take into account stochastic components of the polar tides. Fluctuations excited at frequencies close to the Chandler frequency are analyzed using observations of sea level and the gravitional acceleration. Equations describing the correlation characteristics of the polar motions are presented. [ABSTRACT FROM AUTHOR]

Intrinsic cell chirality has been implicated in the left-right (LR) asymmetry of embryonic development. Impaired cell chirality could lead to severe birth defects in laterality. Previously, we detected cell chirality with an in vitro micropatterning system. Here, we demonstrate for the first time that chirality can be quantified as the coordination of multiaxial polarization of individual cells and nuclei. Using an object labeling, connected component based method, we characterized cell chirality based on cell and nuclear shape polarization and nuclear positioning of each cell in multicellular patterns of epithelial cells. We found that the cells adopted a LR bias the boundaries by positioning the sharp end towards the leading edge and leaving the nucleus at the rear. This behavior is consistent with the directional migration observed previously on the boundary of micropatterns. Although the nucleus is chirally aligned, it is not strongly biased towards or away from the boundary. As the result of the rear positioning of nuclei, the nuclear positioning has an opposite chirality to that of cell alignment. Overall, our results have revealed deep insights of chiral morphogenesis as the coordination of multiaxial polarization at the cellular and subcellular levels. [ABSTRACT FROM AUTHOR]

We have analyzed the geometric characteristics of sunspots. The form of sunspots has been studied by sunspot image normalization to obtain the average profile of spots and the profile relative to the position of cores. The deviation of the sunspot form from the axisymmetric configuration has been studied. We have found that the spots of leading and trailing polarities have a drop shape. The cores of leading and trailing sunspots are shifted toward the western and eastern edges of the photosphere-penumbra boundary, respectively. The strength of the magnetic field of the cores of leading spots in the eastern hemisphere exceeds the field strength in the western hemisphere. We considered the tilt of the form of sunspots as a function of size. The form of spots of a large area ( S > 1000 ppm of solar hemisphere) is elongated along the magnetic axis of the bipole of a group of sunspots. [ABSTRACT FROM AUTHOR]

A new exact analytical solution of the magnetohydrostatic problem describes the equilibrium of a solitary, dense-cool solar filament maintained against the gravity by magnetic force in hot solar corona at heights up to 20-40 Mm. The filament is assumed to be uniform along the axis (the translation symmetry). The magnetic field of the filament has the helical structure (magnetic flux rope) with a typical strength of a few Gauss in the region of minimal temperature (about 4000 K). The model can be applied to the quiescent prominence of both normal and inverse magnetic polarity. [ABSTRACT FROM AUTHOR]

The formation of electrically charged zones during the interaction of strain waves in an initially electroneutral plastic is considered. Experiments were performed on a vinyl plastic rod. The waves were excited by an impact by a bullet in the form a shorter organic glass or vinyl plastic rod against the end the rod. The experimental results have been compared with the proposed mathematical description. [ABSTRACT FROM AUTHOR]

We study the spatial-temporal evolution of a coronal hole and compare it with that of the solar global magnetic field in Cycles 21 - 23 (1976 - 2012). We also analyze the latitude-longitude distribution dynamics of coronal holes and the regularities in the global magnetic field associated with the solar polar field reversal. Polar and non-polar coronal hole populations are considered. The investigation reveals some temporal and spatial regularities in coronal hole distributions that match the global magnetic-field cycle evolution well. The results show that the non-polar coronal hole longitudinal distribution follows all configuration changes in the global magnetic-field structure. Reorganizations of the global magnetic field and coronal hole distributions occur simultaneously during a time interval of a few solar rotations. The cycle evolution of the non-polar coronal holes reflects the transition of the solar global magnetic field from the zonal structure to sectorial and vice versa. Two different types of waves of non-polar coronal holes are revealed from their latitudinal distribution. The first are short poleward waves. They trace the poleward motion of the unipolar photospheric magnetic fields from approximately $35^{\circ}$ to the associated pole in each hemisphere and the redevelopment of a new-polarity polar CH. Although they start the poleward movement before the change of the polar magnetic field in the associated hemisphere, they reach the pole after the polar reversal. The other type of non-polar CH wave forms two sinusoidal branches associated with the positive- and negative-polarity magnetic fields. The complete period of the wave is equal to $\approx268~\mbox{CRs}$ (22 years). These wave CHs arrive at high latitudes during declining phases when the new-polarity polar CHs are already completely formed. [ABSTRACT FROM AUTHOR]

The available paleomagnetic data on the Verkhnyaya Lena Group from different areas of the southern Siberian Platform are revised. The group rests unconformably upon the Lower Cambrian strata and is overlain by Lower Ordovician rocks, which determines conditionally the age of its red-colored deposits. Paleomagnetic correlation of composite sections through the region using defined zones of normal and reversed magnetic polarity serves as a basis for development of the magnetostratigraphic scale for the Verkhnyaya Lena Group. The scale includes nine magnetic zones, which play the role of markers; seven of them are traceable in all the examined sections of the southern Siberian Platform. By the distribution of zones with normal (N) and reversed (R) polarity, the magnetostratigraphic scale is subdivided into three parts. Its lower part is represented by reversed polarity, which is characteristic of the second half of the Lower Cambrian. The middle part is characterized by frequently alternating zones with normal and reversed polarity corresponding to the Middle Cambrian. The upper part of the scale corresponds to the interval of reversed polarity characteristic of the Upper Cambrian and Lower Ordovician. The Middle-Upper Cambrian boundary is located near the last N-R reversal of the geomagnetic field in the Cambrian. The magnetostratigraphic scale includes nine orthozones united into three superzones, which are attributed to two hyperzones of magnetic polarity. [ABSTRACT FROM AUTHOR]

We consider a method of control over the operating frequency of a resonator on bulk acoustic waves, which is based on the selective excitation of eigenmodes. The frequency switching is achieved by using several layers of a ferroelectric in the paraelectric state and applying a control voltage of appropriate magnitude and polarity to each layer. The principle of selectivity is formulated and the criterion function is defined, which ensure the most effective excitation of a selected eigenmode with the possible suppression of parasitic modes. An example of using this function for a resonator switched between four eigenmodes is presented. [ABSTRACT FROM AUTHOR]

Obliquely propagating electron-acoustic solitary waves (EASWs) in a magnetized electron−positron−ion plasma (containing nonextensive hot electrons and positrons, inertial cold electrons, and immobile positive ions) are precisely investigated by deriving the Zakharov-Kuznetsov equation. It is found that the basic features (viz. polarity, amplitude, width, phase speed, etc.) of the EASWs are significantly modified by the effects of the external magnetic field, obliqueness of the system, nonextensivity of hot positrons and electrons, ratio of the hot electron temperature to the hot positron temperature, and ratio of the cold electron number density to the hot positron number density. The findings of our results can be employed in understanding the localized electrostatic structures and the characteristics of EASWs in various astrophysical plasmas. [ABSTRACT FROM AUTHOR]

Shadows are powerful cues in the perception of shapes. We can perceive shading and cast shadow implicitly. We investigated infants' ability to detect a single discrepant figure that was depicted by shading or cast shadow and examined the influence of the contrast polarity of shadows on this process. In Experiment 1, we manipulated the blur direction of a shadow to create stimuli that appeared either to be partially shaded or to cast a shadow and then used a preference to test whether this difference would allow 5- to 8-month-old infants to discriminate the figures that adults were able to perceive as different shapes. Only 7- to-8-month-old infants could differentiate one shading figure from cast shadow figures, and vice versa. In Experiment 2, we reversed the contrast polarity of the figure (dark object with a light shadow) and tested whether discrimination was affected. As has been found with adults, infants exposed to this condition were unable to discriminate the contrast-reversed shading and cast shadow figures. Our results suggested that an age of around 7 months is important for development of the ability to perceive shape differences from shading and cast shadows. [ABSTRACT FROM AUTHOR]

Spectral and photophysical properties of several phenalenone dyes were investigated in the dependence on a type of the polyurethane polymer matrix. The increase in polarity of the solid-state medium was shown to shift absorption and luminescence spectra to the low energy side. Effects of the substituents in the phenalenone chromophore on a Stokes shift value were studied. Photophysical properties of phenalenones were found out to be significantly dependent on the polymerization method of polymer matrices. Considerable growth in photostability of organic dyes was observed when the dyes were bonded covalently with a polymer chain. [ABSTRACT FROM AUTHOR]

We use the recorded seismicity, confined to the Dead Sea basin and its boundaries, by the Dead Sea Integrated Research (DESIRE) portable seismic network and the Israel and Jordan permanent seismic networks for studying the mechanisms of earthquakes in the Dead Sea basin. The observed seismicity in the Dead Sea basin is divided into nine regions according to the spatial distribution of the earthquakes and the known tectonic features. The large number of recording stations and the adequate station distribution allowed the reliable determinations of 494 earthquake focal mechanisms. For each region, based on the inversion of the observed polarities of the earthquakes, we determine the focal mechanisms and the associated stress tensor. For 159 earthquakes, out of the 494 focal mechanisms, we could determine compatible fault planes. On the eastern side, the focal mechanisms are mainly strike-slip mechanism with nodal planes in the N-S and E-W directions. The azimuths of the stress axes are well constrained presenting minimal variability in the inversion of the data, which is in agreement with the Eastern Boundary fault on the east side of the Dead Sea basin and what we had expected from the regional geodynamics. However, larger variabilities of the azimuthal and dip angles are observed on the western side of the basin. Due to the wider range of azimuths of the fault planes, we observe the switching of σ and σ or the switching of σ and σ as major horizontal stress directions. This observed switching of stress axes allows having dip-slip and normal mechanisms in a region that is dominated by strike-slip motion. [ABSTRACT FROM AUTHOR]

The data that describe the long-term reversing behavior of the geodynamo show strong and sudden changes in magnetic reversal frequency. This concerns both the onset and the end of superchrons and most probably the occurrence of episodes characterized by extreme geomagnetic reversal frequency (>10-15 rev./Myr). To account for the complexity observed in geomagnetic reversal frequency evolution, we propose a simple scenario in which the geodynamo operates in three distinct reversing modes: i-a 'normal' reversing mode generating geomagnetic polarity reversals according to a stationary random process, with on average a reversal rate of ∼3 rev./Myr; ii-a non-reversing 'superchron' mode characterizing long time intervals without reversal; iii-a hyper-active reversing mode characterized by an extreme geomagnetic reversal frequency. The transitions between the different reversing modes would be sudden, i.e., on the Myr time scale. Following previous studies, we suggest that in the past, the occurrence of these transitions has been modulated by thermal conditions at the core-mantle boundary governed by mantle dynamics. It might also be possible that they were more frequent during the Precambrian, before the nucleation of the inner core, because of a stronger influence on geodynamo activity of the thermal conditions at the core-mantle boundary. [ABSTRACT FROM AUTHOR]

Polarity reversals may occur to transmitted P waves if the incidence angle is greater than the critical incidence angle. We analyze the characteristics of reflection and transmission coefficients under the condition of wide incidence angle based on Zoeppritz equations. We find that for specific conditions, as the incidence angle increases, the characteristic curve of the transmitted P-wave coefficient enters the third quadrant from the first quadrant through the origin, which produces a transition in the transmitted P wave and the corresponding coefficient experiences polarity reversal. We derive the incidence angle when the transmitted P-wave coefficient is zero and verify that it equals zero by using finite-difference forward modeling for a single-interface model. We replace the water in the model reservoir by gas and see that the reservoir P-wave velocity and density decrease dramatically. By analyzing the synthetic seismogram of the transmitted P wave in the single-interface model, we show that the gas-saturated reservoir is responsible for polarity reversal. [ABSTRACT FROM AUTHOR]

A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on 2012 July 1 (SOL2012-07-01) in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade ( ${\approx}\,40~\%$). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions. [ABSTRACT FROM AUTHOR]

This is the first-ever study to determine the focal mechanisms for very small volcanic earthquakes (magnitudes approximately 1). We used a swarm of small volcanic earthquakes in the Koryakskii Volcano area during the seismic precursory period before the eruption (March to December 2008) and during the subsequent volcanic activity (December 28, 2008 through April 2009). Statistically significant estimates of mechanism parameters were found for the volcanic earthquakes in this swarm. The mechanisms were determined using the polarities of the first motions of P-waves. The resulting rupture planes strike along azimuths that are consistent with the fault plane of the nearly north-south zone where the 2008-2009 seismicity of Koryakskii Volcano occurred. It was shown that the earthquakes in and around the fault zone can be classified into those south of the Koryakskii summit (zone I) and north of it (zone II). The azimuths of rupture planes in zones I and II are significantly different (212° ± 12° and 5° ± 12°, respectively). [ABSTRACT FROM AUTHOR]

As an observational case study, we consider the origin of a prominent poleward surge of leading polarity, visible in the magnetic butterfly diagram during Solar Cycle 24. A new technique is developed for assimilating individual regions of strong magnetic flux into a surface-flux transport model. By isolating the contribution of each of these regions, the model shows the surge to originate primarily in a single high-latitude activity group consisting of a bipolar active region present in Carrington Rotations 2104 - 05 (November 2010 - January 2011) and a multipolar active region in Rotations 2107 - 08 (February - April 2011). This group had a strong axial dipole moment opposed to Joy's law. On the other hand, the modelling suggests that the transient influence of this group on the butterfly diagram will not be matched by a large long-term contribution to the polar field because it is located at high latitude. This is in accordance with previous flux-transport models. [ABSTRACT FROM AUTHOR]

The dynamics of ionization processes in high-pressure nitrogen, air, and SF during breakdown of a gap with a nonuniform distribution of the electric field by nanosecond high-voltage pulses was studied experimentally. Measurements of the amplitude and temporal characteristics of a diffuse discharge and its radiation with a subnanosecond time resolution have shown that, at any polarity of the electrode with a small curvature radius, breakdown of the gap occurs via two ionization waves, the first of which is initiated by runaway electrons. For a voltage pulse with an ∼500-ps front, UV radiation from different zones of a diffuse discharge is measured with a subnanosecond time resolution. It is shown that the propagation velocity of the first ionization wave increases after its front has passed one-half of the gap, as well as when the pressure in the discharge chamber is reduced and/or when SF is replaced with air or nitrogen. It is found that, at nitrogen pressures of 0.4 and 0.7 MPa and the positive polarity of the high-voltage electrode with a small curvature radius, the ionization wave forms with a larger (∼30 ps) time delay with respect to applying the voltage pulse to the gap than at the negative polarity. The velocity of the second ionization wave propagating from the plane electrode is measured. In a discharge in nitrogen at a pressure of 0.7 MPa, this velocity is found to be ∼10 cm/ns. It is shown that, as the nitrogen pressure increases to 0.7 MPa, the propagation velocity of the front of the first ionization wave at the positive polarity of the electrode with a small curvature radius becomes lower than that at the negative polarity. [ABSTRACT FROM AUTHOR]

The dependence of the crystallographic polarity of GaN epitaxial layers produced by nitrogen plasma-enhanced molecular-beam epitaxy on Si(111) substrates on the nitridation parameters and initial growth conditions has been studied. A rapid procedure for determining the polarity of GaN epitaxial layers was developed. It was found experimentally that the nitridation parameters of the silicon substrate have no effect on the polarity of a GaN layer. It was shown that the substrate temperature in the stage of nucleation of a GaN epitaxial layer is one of the factors determining its polarity. [ABSTRACT FROM AUTHOR]

A nickel-based high-temperature alloy widely used in aerospace engines is a typical difficult-to-cut material by conventional machining processes due to its high-temperature mechanical strength and toughness. Blasting erosion arc machining (BEAM), a new type of electrical discharge machining (EDM) method, is capable of removing such materials with a very high material removal rate and a low tool wear ratio. This paper presents experimental investigations in machining characteristics and machined surface integrity of the nickel-based alloy GH4169 (similar to Inconel718) by positive polarity blasting erosion arc machining (positive BEAM). The test results imply a possibility to improve the surface integrity with positive BEAM compared with a regular negative one. In this work, a three-factor, three-level machining performance experiment was carried out to examine the effects of the machining parameters such as discharge peak current, flushing inlet pressure, and pulse duration on the machining performances of material removal rate, tool wear ratio, and surface roughness. The experimental results show that positive BEAM is capable of greatly improving the machined surface integrity. The surface roughness decreased from 274 μm (under negative polarity BEAM) down to 31 μm (under positive polarity BEAM). Additionally, fewer micro-cracks and a thinner heat-affected zone on the workpiece surface can be observed. It also reveals that by optimizing the combination of the negative and the positive BEAM, favorable machining performances of high material removal rate and finer surface roughness are possible. By utilizing the polarity effects, the machining allowance for the subsequent semi-finishing processes such as cutting can be further reduced. [ABSTRACT FROM AUTHOR]

Unique, hollow, micron-sized polystyrene (PS) particles having lots of dents on the surface, so-called cage-like particles, were obtained by seeded dispersion polymerization of 2-ethylhexyl methacrylate with PS particles stabilized by poly(vinyl alcohol) in the presence of hexadecane droplets. The effect of main parameters (e.g., average molecular weight of seed particles, and stabilizer and initiator type) responsible for acquiring such particles was investigated. The experimental results revealed that cage-like shape is produced because of particle coagulation during polymerization. Moreover, it was observed that changing stabilizer and initiator type, and employing seed particles with low average molecular weight, which all of them contribute in coagulation of particles, result in the fabrication of cage-like shape. [ABSTRACT FROM AUTHOR]

It has been hypothesized that the steady-state response to a periodic sequence of clicks can be modeled as the superposition of responses to single clicks. Here, this hypothesis is challenged by presenting an extra click halfway between two consecutive clicks of a regular series, while measuring the auditory evoked field. After a solitary click at time zero, the click series sounded from 100 to 900 ms, with the extra click presented around 500 ms. The silent period between two stimulus sequences was 310-390 ms (uniformly distributed) so that one stimulation cycle lasted, on average, 1250 ms. Five different click rates between 20 and 60 Hz were examined. The disturbance caused by the extra click was revealed by subtracting the estimated steady-state response from the joint response to the click series and the extra click. The early peaks of the single-click response effectively coincide with same-polarity peaks of the 20-Hz steady-state response. Nevertheless, prediction of the latter from the former proved impossible. However, the 40-Hz steady-state response can be predicted reasonably well from the 20-Hz steady-state response. Somewhat surprisingly, the amplitude of the evoked response to the extra click grew when the click rate of the train was increased from 20 to 30 Hz; the opposite effect would have been expected from research on adaptation. The smaller amplitude at lower click rates might be explained by forward suppression. In this case, the apparent escape from suppression at higher rates might indicate that the clicks belonging to the periodic train are being integrated into an auditory stream, possibly in much the same manner as in classical stream segregation experiments. [ABSTRACT FROM AUTHOR]

The distribution of the paleointensities and the lengths of geomagnetic polarity intervals (time intervals between the successive reversals of the Earth's magnetic field) corresponding to the different geological epochs was studied. It was found that the stochastic series of paleointensities in most cases are best approximated by the power-law function. The exponents of the power-law distributions vary depending on the intervals of the geological time that accommodate the analyzed paleomagnetic data. The distributions of the lengths of polarity intervals are approximated by the exponential function. The exponents varied depending also on the intervals of the geological time. The analysis shows that the most significant changes in the behavior of paleointensity occurred in the Paleogene near the Paleocene-Eocene boundary. Based on the analysis of the paleomagnetic data, it is hypothesized that turbulence of the magnetoactive medium played an important role in the generation of the Earth's magnetic field. The turbulence of the magnetoactive medium increased in the Cretaceous compared to the Jurassic and Paleogene. [ABSTRACT FROM AUTHOR]

Elongated magnetic polarities are observed during the emergence phase of bipolar active regions (ARs). These extended features, called magnetic tongues, are interpreted as a consequence of the azimuthal component of the magnetic flux in the toroidal flux-tubes that form ARs. We develop a new systematic and user-independent method to identify AR tongues. Our method is based on determining and analyzing the evolution of the AR main polarity inversion line (PIL). The effect of the tongues is quantified by measuring the acute angle [ τ] between the orientation of the PIL and the direction orthogonal to the AR main bipolar axis. We apply a simple model to simulate the emergence of a bipolar AR. This model lets us interpret the effect of magnetic tongues on parameters that characterize ARs ( e.g. the PIL inclination and the tilt angles, and their evolution). In this idealized kinematic emergence model, τ is a monotonically increasing function of the twist and has the same sign as the magnetic helicity. We systematically apply our procedure to a set of bipolar ARs (41 ARs) that were observed emerging in line-of-sight magnetograms over eight years. For most of the cases studied, the tongues only have a small influence on the AR tilt angle since tongues have a much lower magnetic flux than the more concentrated main polarities. From the observed evolution of τ, corrected for the temporal evolution of the tilt angle and its final value when the AR is fully emerged, we estimate the average number of turns in the subphotospherically emerging flux-rope. These values for the 41 observed ARs are below unity, except for one. This indicates that subphotospheric flux-ropes typically have a low amount of twist, i.e. highly twisted flux-tubes are rare. Our results demonstrate that the evolution of the PIL is a robust indicator of the presence of tongues and constrains the amount of twist in emerging flux-tubes. [ABSTRACT FROM AUTHOR]

We investigate the atmospheric response to a small emerging flux region (EFR) that occurred in the positive polarity of Active Region 11236 on 23 - 24 June 2011. Data from the Solar Dynamics Observatory's Atmospheric Imaging Assembly (AIA), the Helioseismic and Magnetic Imager (HMI), and Hinode's EUV imaging spectrometer (EIS) are used to determine the atmospheric response to new flux emerging into a pre-existing active region. Brightenings are seen forming in the upper photosphere, chromosphere, and corona over the EFR location whilst flux cancellation is observed in the photosphere. The impact of the flux emergence is far reaching, with new large-scale coronal loops forming up to 43 Mm from the EFR and coronal upflow enhancements of approximately 10 km s on the north side of the EFR. Jets are seen forming in the chromosphere and the corona over the emerging serpentine field. This is the first time that coronal jets have been seen over the serpentine field. [ABSTRACT FROM AUTHOR]

A change in the ratio of the intensities of particles of high-energy cosmic rays arriving from the North and South in the time interval of 2010-2014 has been detected with a calorimeter entering into the experimental complex of the PAMELA satellite experiment since June 2006. The polarity of the magnetic field of the Sun changed in a part of this time interval. Thus, the results indicate that the North-South asymmetry of cosmic ray fluxes is related to the magnetic field of the Sun. [ABSTRACT FROM AUTHOR]

Equations that are used for the calculation and distributions of the electrical voltage U( t) output from a magnetic-field transducer as it scans a discrete magnetic medium with recorded residual magnetic fields, which were produced in it by acting individual magnetic-field pulses with opposite-polarity surges, are reported. The distributions were obtained via the Delphi programming language. The phenomenon of hysteretic interference ( HI) of a magnetic field, which allows one to increase the accuracy of measurements, is used for the inspection of objects made from electrocoductive and magnetic materials. [ABSTRACT FROM AUTHOR]

The article discusses geomagnetic reversal and the consequences that may occur due to this problem. Topics discussed include relationship of magnetic field and geomagnetic reversal, geomagnetic field polarity, and magnetic field excursions. Also discussed is the analysis of Late Cretaceous–Cenozoic (C-sequence).

The self-similar expansion method is applied on the fluid system of equations which describes a plasma system consisting of opposite polarity dust grains, positive ions and electrons. The resultant system of equations is solved numerically to study the properties of the plasma expansion of this system. It is found that the presence of the second species of the dust has a great effect on the properties of the expansion of the other species. [ABSTRACT FROM AUTHOR]

Propagation of nonlinear dust-acoustic waves in a magnetized collisionless plasma having positively, negatively charged dust grains and nonextensive distributed electrons and ions has been investigated. A reductive perturbation method is used to obtain a nonlinear Korteweg-de Vries (KdV) equation describing the model. The dynamics of the modulational instability gives rise to the formation of rogue waves that is described by a nonlinear Schrödinger equation. The dependence of rogue waves profiles on positive and negative charged dust cyclotron frequencies, nonextensive parameters of electrons and ions is investigated numerically. The result of the present investigation may be applicable to some plasma environments, such as cometary tails and upper mesosphere. [ABSTRACT FROM AUTHOR]

We consider the motion of high-energy charged particles (cosmic rays) in Parker's spiral magnetic field. We show that under radial particle ejection from a sphere outside which there is Parker's magnetic field, all of the particles escaping from the sphere are focused either along the field symmetry axis or in the equatorial plane, depending on the field polarity. Based on the results obtained, we propose a possible model that explains the origin of relativistic jets. [ABSTRACT FROM AUTHOR]

When magnetic flux emerges from beneath the photosphere, it displaces the preexisting field in the corona, and a current sheet generally forms at the boundary between the old and new magnetic domains. Reconnection in the current sheet relaxes this highly stressed configuration to a lower energy state. This scenario is most familiar and most often studied in flares, where the flux transfer is rapid. We present here a study of steady, quiescent flux transfer occurring at a rate three orders of magnitude lower than that in a large flare. In particular, we quantify the reconnection rate and the related energy release that occurred as the new polarity emerged to form NOAA Active Region 11112 ( SOL16 October 2010T00:00:00L205C117) within a region of preexisting flux. A bright, low-lying kernel of coronal loops above the emerging polarity, observed with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory and the X-ray Telescope onboard Hinode, originally showed magnetic connectivity only between regions of newly emerged flux when overlaid on magnetograms from the Helioseismic and Magnetic Imager. Over the course of several days, this bright kernel advanced into the preexisting flux. The advancement of an easily visible boundary into the old flux regions allows measuring the rate of reconnection between old and new magnetic domains. We compare the reconnection rate with the inferred heating of the coronal plasma. To our knowledge, this is the first measurement of steady, quiescent heating related to reconnection. We determined that the newly emerged flux reconnects at a fairly steady rate of 0.38×10 Mx s over two days, while the radiated power varies between (2 - 8)×10 erg s over the same time. We found that as much as 40 % of the total emerged flux at any given time may have reconnected. The total amounts of transferred flux (∼ 1×10 Mx) and radiated energy (∼ 7.2×10 ergs) are comparable to that of a large M- or small X-class flare, but are stretched out over 45 hours. [ABSTRACT FROM AUTHOR]

The algorithms and neural circuits that process spatio-temporal changes in luminance to extract visual motion cues have been the focus of intense research. An influential model, the Hassenstein-Reichardt correlator, relies on differential temporal filtering of two spatially separated input channels, delaying one input signal with respect to the other. Motion in a particular direction causes these delayed and non-delayed luminance signals to arrive simultaneously at a subsequent processing step in the brain; these signals are then nonlinearly amplified to produce a direction-selective response. Recent work in Drosophila has identified two parallel pathways that selectively respond to either moving light or dark edges. Each of these pathways requires two critical processing steps to be applied to incoming signals: differential delay between the spatial input channels, and distinct processing of brightness increment and decrement signals. Here we demonstrate, using in vivo patch-clamp recordings, that four medulla neurons implement these two processing steps. The neurons Mi1 and Tm3 respond selectively to brightness increments, with the response of Mi1 delayed relative to Tm3. Conversely, Tm1 and Tm2 respond selectively to brightness decrements, with the response of Tm1 delayed compared with Tm2. Remarkably, constraining Hassenstein-Reichardt correlator models using these measurements produces outputs consistent with previously measured properties of motion detectors, including temporal frequency tuning and specificity for light versus dark edges. We propose that Mi1 and Tm3 perform critical processing of the delayed and non-delayed input channels of the correlator responsible for the detection of light edges, while Tm1 and Tm2 play analogous roles in the detection of moving dark edges. Our data show that specific medulla neurons possess response properties that allow them to implement the algorithmic steps that precede the correlative operation in the Hassenstein-Reichardt correlator, revealing elements of the long-sought neural substrates of motion detection in the fly. [ABSTRACT FROM AUTHOR]

Pulse characteristics of single barrier discharges as well as parameters of charges accumulated on the surface of a dielectric under the atmospheric pressure in the 'needle-(0.1-2.0)-mm air gap-polymer barrier-plane' system are investigated. It is found experimentally that for the positive polarity of the needle, the voltage for the discharge initiation is higher than in the case of the negative polarity by ∼25-35%. The reversal of the needle polarity from negative to positive increases the amplitude of the discharge current and the accumulated surface charge by ∼1.5-3 times. For the positive polarity of the needle, the discharge is governed by a streamer mechanism, while for the negative polarity, the discharge is initiated by the formation of a single Trichel pulse. The single pulse regime is observed for the discharge current up to a certain electrode gap d. For the positive needle and for air gap width d > d ≈ 1.5 mm, a multipulse burst corona is formed, while for the negative needle and d > d ≈ 0.9 mm, a damped sequence of Trichel pulses evolves in the system. [ABSTRACT FROM AUTHOR]

Our investigation has been carried using the instruments onboard the Solar Dynamics Observatory (SDO) providing a high resolution of images (AIA photographs and HMI magnetograms). We have investigated the structure and magnetic evolution of several coronal bright points and small scale N-S polarity magnetic fluxes closely associated with them. We also compare the evolution of the magnetic polarities of elementary isolated sources of positive and negative fluxes (magnetic bipoles) and coronal bright points. Tiny ('elementary') coronal bright points have been detected. A standard coronal bright point is shown to be a group of 'elementary' coronal bright points that flare up sequentially. Our investigation shows that a change in the magnetic fluxes of opposite polarities is observed before the flare of a coronal bright point. We show that not all cases of the formation of coronal bright points are described by the magnetic reconnection model. This result has not been considered previously and has not been pointed out by other authors. [ABSTRACT FROM AUTHOR]