Polarity Time Research Articles

Theoretical and experimental analysis of circularly polarized luminescence spectrophotometers for artifact-free measurements using a single CCD camera

Circularly polarized luminescence (CPL) is a fast growing research field as a complementary chiroptical spectroscopy alternative to the conventional circular dichroism or in the quest of devices producing circularly polarized light for different applications. Because chiroptical signals are generally lower than 0.1%, conventional chiral spectroscopies rely on polarization time modulation requiring step-by-step wavelength scanning and a long acquisition time. High throughput controls motivated the development of CPL spectrophotometers using cameras as detectors and space polarization splitting. However, CPL measurements imposes careful precautions to minimize the numerous artifacts arising from experimental imperfections. Some previous work used complex calibration procedure to this end. Here we present a rigorous Mueller analysis of an instrument based on polarizations space splitting. We show that by using one camera and combining spatial and temporal separation through two switchable circular polarization encoding arms we can record accurate CPL spectra without the need of any calibration. The measurements robustness and their fast acquisition times are exemplified on different chiral emitters.

Charophyte flora from the Oligocene fossil site of Suceag (Transylvanian Basin, Romania)

A charophyte assemblage composed of six species has been recovered from lower Oligocene deposits of the Dâncu Formation at the fossil site of Suceag (Transylvanian Basin, Romania). The assemblage is dominated by the two varieties of the species Lychnothamnus pinguis (L. pinguis forma pinguis and L. pinguis forma major). Accessory species include Lychnothamnus prealangeri, Nitellopsis (Tectochara) merianii, and few Sphaerochara sp. and Harrisichara sp. gyrogonites. L. pinguis is the index species of the homonymous Rupelian European biozone which was previously correlated in Western Europe with the Mammal Paleogene Reference Levels of MP21–MP23, and calibrated with the Geomagnetic Polarity Time Scale (GPTS), chrones C13N and C12R. From a paleobiogeographic viewpoint, this study confirms the presence of L. pinguis forma pinguis and L. praelangeri in Romania and in the whole Eastern Europe. Moreover, the charophyte assemblage from Suceag belongs to the Priabonian–Rupelian European charophyte bioprovince. While the vertebrate fossils reported in the same fossil locality indicate that the Dâncu Formation at Suceag sedimented in an estuarine environment, the charophyte assemblage suggests a more complex pattern, with presence of freshwater lakes too.

Comments on: “Ambiguity in induced polarization time constants and the advantage of the Pelton model” (Andreas Weller and Lee Slater, 2022, Geophysics, 87, no. 6, E393–E399)

SUMMARY The underlying Cole-Cole model of the frequency dependence of complex conductivity and resistivity predicts two time constants that are not identical but which are related to each other. The shorter time constant [Formula: see text] predicts the current response to a voltage step and, in various models of a mineralized grain, is related to the intrinsic properties of the polarizable component, whereas the longer time constant [Formula: see text], which predicts the voltage response to a current step, is dependent on intrinsic material properties and also the relative volume of polarizable material as defined through chargeability. As a consequence, although we agree with most of the conclusions of the original paper, the specification [Formula: see text] instead of [Formula: see text] in reference tables will simplify.

Sub-Nanosecond Switching of Si:HfO2 Ferroelectric Field-Effect Transistor.

The discovery of ferroelectric doped HfO2 enabled the emergence of scalable and CMOS-compatible ferroelectric field-effect transistor (FeFET) technology which has the potential to meet the growing need for fast, low-power, low-cost, and high-density nonvolatile memory, and neuromorphic devices. Although HfO2 FeFETs have been widely studied in the past few years, their fundamental switching speed is yet to be explored. Importantly, the shortest polarization time demonstrated to date in HfO2-based FeFET was ∼10 ns. Here, we report that a single subnanosecond pulse can fully switch HfO2-based FeFET. We also study the polarization switching kinetics across 11 orders of magnitude in time (300 ps to 8 s) and find a remarkably steep time-voltage relation, which is captured by the classical nucleation theory across this wide range of pulse widths. These results demonstrate the high-speed capabilities of FeFETs and help better understand their fundamental polarization switching speed limits and switching kinetics.

Source localized modelling to estimate the depth of anisotropy beneath eastern Himalaya using spatial coherency of shear-wave splitting parameters

The present study focuses on the source localization and depth estimation of anisotropy beneath the eastern Himalaya ranging from Nepal in the west to Eastern Himalayan Syntaxis at the north eastern flank of the Indian region. Although previous literatures on anisotropy suggest the possible deformation patterns and their mechanisms beneath the eastern Himalayan region, a compressive analysis of the source and depth localization of anisotropy is missing, which is addressed in tghis study. A comprehensive analysis of the central depth of anisotropy beneath this complex orogeny is carried out using the Spatial coherency method. This technique is based on the Fresnel-zone principle with a more generalized use of variation factor as a function of fast axis polarization and delay time beneath a particular station. A total of 435 splitting measurements from the entire eastern Himalayan region are utilized to model the anisotropy source localization and depth estimation beneath three major tectonic domains like Nepal Himalaya, Arunachal Himalaya and the Eastern Himalayan Syntaxis to understand the source of anisotropy and the deformation mechanism. Spatial coherency analysis of splitting parameters beneath the Nepal Himalaya suggests that the source of anisotropy is at about 180 km depth, which coincides with the region's lithosphere-asthenosphere boundary (LAB). This emphasizes the asthenospheric source in controlling the deformation parallel to the absolute plate motion (APM) of the Indian plate. For both the Arunachal Himalaya and the Eastern Himalaya Syntaxis, the source of anisotropy corresponds to the depth of 135 km and 150 km respectively, suggestive of a lithospheric source in dominating the deformation patterns in these regions.

On Surface Resistivity Measurements of Thin Insulation Materials

Surface resistivity measurements are frequently used for material characterization. However, the influence of sample thickness is not covered sufficiently in ASTM D257 and IEC 62631-3-2 standards. In this work, electric field simulations and polarization–depolarization current (PDC) measurements are used to study the thickness dependence of such measurements. It is found that measurements according to the standards are not reasonable for low thickness (<1 mm) and high surface resistivity (>1013– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{14}}~ {\Omega } $ </tex-math></inline-formula> ). The dependence on thickness is shown to be mainly due to the different tangential electric field stress along the measured surface. Furthermore, indications for charge injection at high electric field stress inside the sample volume are found by a positive polarity of the depolarization currents. A novel electrode configuration for more accurate (more than one order of magnitude) and much less thickness-dependent surface resistivity measurements is proposed in this work and its benefits are demonstrated. It is also shown how the parasitic influence of an electrode holder can be effectively reduced by more than one order of magnitude when measuring surface resistivities. In addition, it is found that polarization times for steady-state surface resistivity values should be at least several minutes instead of the suggested 60 s from standards.

Late Miocene to Present Paleoclimatic and Paleoenvironmental Evolution of the South China Sea Recorded in the Magneto‐Cyclostratigraphy of IODP Site U1505

AbstractThe continuous sedimentary cores recovered at the International Ocean Discovery Program (IODP) Site U1505, Expedition 368, provide an opportunity for paleoceanography and paleoclimate reconstruction in the continental margin of the northern South China Sea (SCS). In this study, we conducted detailed rock‐ and paleomagnetic studies on 420 discrete samples from the top ∼200 m of the synthetic records of Holes U1505C and U1505D. Rock magnetic analyses indicate that low‐coercivity pseudosingle domain magnetite dominates as the primary ferromagnetic mineral of Site U1505. The magnetostratigraphic age model was constructed by correlating the interpreted polarity sequence with the Geomagnetic Polarity Time Scale 2020 with the constraints of the biostratigraphic data and the distribution probability of the age of each polarity zone provided by a Dynamic Time Warping algorithm. The Milankovitch cycles of the short eccentricity, obliquity, and precession cycles were identified in the magnetic susceptibility (MS) and natural gamma radiation (NGR) series based on paleomagnetic results. We established an ∼9 Myr high‐resolution astronomical time scale by tuning the MS and NGR records to the global oxygen isotope curves, the obliquity, and the eccentricity curves of the La2004 astronomical solution. Our new age model reveals detailed sedimentation rate variations and a ∼500 kyr hiatus across the Brunhes‐Matuyama boundary related to local tectonic activity. These results lay the foundation for understanding the paleoceanography and paleoclimate evolution of the SCS.

Turkey as a restrained middle power

ABSTRACT Recent years have witnessed increasing questions regarding Turkey’s international orientation. Many have defined Turkey as an over-ambitious middle power, a categorization similar to traditional middle power identity, yet also evincing a strong determination on the part of Turkish decision makers to transform Turkey into a regional power that has the potential to become a great power sometime in future. This essay examines why Turkey’s over-ambitious middle power strategy has failed in producing the expected outcomes and why adopting the strategy of restrained middle power will serve Turkey’s national interests much better at a time of great upheavals, polarization, and uncertainties in international politics. The restrained middle power strategy can be justified on both realist and liberal grounds.

Promoting osseointegration of titanium by pH-responsive releasing of H2S and optimizing polarization time for macrophages

To improve the osteointegration of titanium implant by macrophages immunoregulation, in this study, a functionalized titanium implant was fabricated by storing H2S donors (JK-1) into Ti nanotubes and plugging with chitosan/gelatin multilayers. After implantation, the inflammation responses were initiated immediately and overlaps with the subsequent regeneration phase. The acidic inflammatory environment could trigger the degradation of multilayers and release of H2S. By optimizing polarization regulation time of M1 to M2 macrophages, we can maintain the phagocytosis and neovascularization functions of M1 macrophages and improve anti-inflammatory response timely by M2 macrophages polarization. And in turn the immunomodulation of macrophage could lead to the efficient osteogenic differentiation of MSCs. In vivo results showed that keeping M1 macrophages for 2 or 3 days could promote neovascularization around implants. Subsequent M2 macrophages polarization could improve osteogenesis. So, it is a promising strategy for titanium implants improvement was supplied that a better osseointegration of titanium-based implants could be possessed by macrophages immunomodulation.

Study on the Effect of Freeze-Thaw Action on the Electrical Conductivity and Sensing Properties of Graphene-Based Cement Composites.

Graphene can effectively improve the mechanical and electrical properties of cement-based materials due to its excellent tensile strength, thermal conductivity and electrical conductivity. In this paper, the effects of freeze-thaw on the conductivity and sensing properties of graphene-based cement materials were investigated. After the preparation of graphene-based cement materials, they were subjected to different times of freeze-thaw action. The experiments were designed to analyze the influence of freeze-thaw on the electrical conductivity, humidity sensitivity, thermosensitivity and pressure sensitivity of graphene-based cement composites. The results show that the influence of freeze-thaw on the electrical conductivity of graphene is mainly manifested in the influence on the resistivity and the extension of the polarization time, and the influence on the percolation transition zone is small. After freeze-thaw, the polarization time of the specimen decreases with the increase of the relative water content. The temperature has a great influence on the polarization effect of graphene-based cement composites and the composites with graphene content of the zone B still show satisfactory pressure-sensitive property after freeze-thaw.

Storm time polar cap expansion: interplanetary magnetic field clock angle dependence

Abstract. It is well known that the polar cap, delineated by the open–closed field line boundary (OCB), responds to changes in the interplanetary magnetic field (IMF). In general, the boundary moves equatorward when the IMF turns southward and contracts poleward when the IMF turns northward. However, observations of the OCB are spotty and limited in local time, making more detailed studies of its IMF dependence difficult. Here, we simulate five solar storm periods with the coupled model consisting of the Open Geospace General Circulation Model (OpenGGCM) coupled with the Coupled Thermosphere Ionosphere Model (CTIM) and the Rice Convection Model (RCM), i.e., the OpenGGCM-CTIM-RCM, to estimate the location and dynamics of the OCB. For these events, polar cap boundary location observations are also obtained from Defense Meteorological Satellite Program (DMSP) precipitation spectrograms and compared with the model output. There is a large scatter in the DMSP observations and in the model output. Although the model does not predict the OCB with high fidelity for every observation, it does reproduce the general trend as a function of IMF clock angle. On average, the model overestimates the latitude of the open–closed field line boundary by 1.61∘. Additional analysis of the simulated polar cap boundary dynamics across all local times shows that the MLT of the largest polar cap expansion closely correlates with the IMF clock angle, that the strongest correlation occurs when the IMF is southward, that during strong southward IMF the polar cap shifts sunward, and that the polar cap rapidly contracts at all local times when the IMF turns northward.

Estimation of Earth Rotation Parameters and Prediction of Polar Motion Using Hybrid CNN–LSTM Model

The Earth rotation parameters (ERPs), including polar motion (PMX and PMY) and universal time (UT1-UTC), play a central role in functions such as monitoring the Earth’s rotation and high-precision navigation and positioning. Variations in ERPs reflect not only the overall state of movement of the Earth, but also the interactions among the atmosphere, ocean, and land on the spatial and temporal scales. In this paper, we estimated ERP series based on very long baseline interferometry (VLBI) observations between 2011–2020. The results show that the average root mean square errors (RMSEs) are 0.187 mas for PMX, 0.205 mas for PMY, and 0.022 ms for UT1-UTC. Furthermore, to explore the high-frequency variations in more detail, we analyzed the polar motion time series spectrum based on fast Fourier transform (FFT), and our findings show that the Chandler motion was approximately 426 days and that the annual motion was about 360 days. In addition, the results also validate the presence of a weaker retrograde oscillation with an amplitude of about 3.5 mas. This paper proposes a hybrid prediction model that combines convolutional neural network (CNN) and long short-term memory (LSTM) neural network: the CNN–LSTM model. The advantages can be attributed to the CNN’s ability to extract and optimize features related to polar motion series, and the LSTM’s ability to make medium- to long-term predictions based on historical time series. Compared with Bulletin A, the prediction accuracies of PMX and PMY are improved by 42% and 13%, respectively. Notably, the hybrid CNN–LSTM model can effectively improve the accuracy of medium- and long-term polar motion prediction.

On the origin of polarization fatigue and Curie–von Schweidler relaxation current in Pb(Zrx,Ti1−x)O3 ferroelectric thin films: A unique mechanism based on charge trapping by interface defects

This article discusses the widespread problem of polarization fatigue in ferroelectric materials. After a review of the bibliographical data on this topic but also on the older and equally widespread problem of dielectric relaxation in solids, a possible correlation between these two phenomena is established by observing that the decrease with time of polarization obeys the Curie–von Schweidler (CVS) law like the relaxation current. An electrical model involving a charge trapping mechanism by electronic defects in bandgap at the contact/ferroelectric interface is then developed, which simultaneously explains polarization fatigue and relaxation current. The CVS law is found considering interface traps with a continuum of time constants. This study sheds new light on the origin of these phenomena, which remain unexplained to date.

Characterizing interaction of multiple nanocavity confined plasmids in presence of large DNA model nucleoid.

Bacteria have numerous large dsDNA molecules that freely interact within the cell, including multiple plasmids, primary and secondary chromosomes. The cell membrane maintains a micron-scale confinement, ensuring that the dsDNA species are proximal at all times and interact strongly in a manner influenced by the cell morphology (e.g. whether cell geometry is spherical or anisotropic). These interactions lead to non-uniform spatial organization and complex dynamics, including segregation of plasmid DNA to polar and membrane proximal regions. However, exactly how this organization arises, how it depends on cell morphology and number of interacting dsDNA species are under debate. Here, using an in vitro nanofluidic model, featuring a cavity that can be opened and closed in situ, we address how plasmid copy number and confinement geometry alter plasmid spatial distribution and dynamics. We find that increasing the plasmid number alters the plasmid spatial distribution and shortens the plasmid polar dwell time; sharper cavity end curvature leads to longer plasmid dwell times.

The Late Cretaceous alkaline magmatism in the SE Brazilian coast: new paleomagnetic data and age constraints

Alkaline dikes from the Santos-Rio de Janeiro coast, SE Brazil, mainly from São Sebastião and Búzios islands, yielded a Late Cretaceous paleomagnetic pole (SR) located at 319.7°E 81.2°S (N = 44, A95 = 3.0°, k = 44). This pole includes some sites of alkaline stocks from São Sebastião Island of the same age and supersedes the previous pole for this island. To match the available radiometric ages and the prevailing normal polarity remanence of the rocks with the geomagnetic polarity time scale, the SR pole is placed at 84 Myr. Another group of alkaline rocks, dikes located mainly in Rio de Janeiro, was assigned an age of less than 70 Myr. The ages of the Poços de Caldas, Itatiaia, and Passa Quatro paleomagnetic poles are also discussed based on available radiometric data. Assuming a rigid plate, the SR pole indicates the southward movement of about 7° with virtually no rotation between 100 and 84 Myr. From approximately 84 to 70 Myr, a clockwise rotation of 8° is postulated, with slight variation in latitude.

Passivation of precipitation-hardened UNS N07718 in a shallow sour aqueous solution.

Passivation of precipitation-hardened UNS N07718 in 5 wt% NaCl + 0.5 wt% CH3COOH was investigated. Cyclic potentiodynamic polarisation revealed that the alloy surface was passivated without active-passive transition behaviour. The alloy surface was in a stable passive state during potentiostatic polarisation at 0.5 VSSE for 12 h. Bode and Mott-Schottky plots showed that the passive film became electrically resistive and less defective with n-type semiconductive properties during the polarisation. X-ray photoelectron spectra revealed that Cr- and Fe-enriched hydro/oxide layers were formed on the outer and inner layers of the passive film, respectively. The thickness of the film was almost constant with the increase of the polarisation time. The outer Cr-hydroxide layer changed into a Cr-oxide layer during the polarisation, resulting in a decreased donor density in the passive film. The film's composition change during the polarisation should be related to the corrosion resistance of the alloy in the shallow sour conditions.

Global Cities and COVID-19: Stories of Resilience and Fragility in Los Angeles

This paper examines the impact of the COVID-19 pandemic on global cities. In particular, the paper revisits and updates the academic literature on global cities and focuses on the discussion of the resilience and fragility of global cities in light of an unprecedented global pandemic. By severely testing the strength and durability of the international flow of goods and people, the sweeping scale and intensity of the COVID-19 pandemic directly called into question the thick and complicated network of global cities that serve as modes for international trade and travel. The paper then draws on the impact of COVID-19 on Los Angeles to examine how the pandemic impacted the city’s health, economy, and social fabric. The findings suggest that the international connections of Los Angeles became a source of initial vulnerability but eventual strength as the city managed the health and the economic impacts of the pandemic. However, more complicated stories emerge from immigrant and ethnic communities in Los Angeles. For this “Ethnic Los Angeles,” COVID-19 came to the United States at a time of intense political polarization and severe economic inequality. This polarization and inequality have contributed to Ethnic Los Angeles bearing an unfair share of the burden from the pandemic.

Identification and quantification of the distributed capacitance and ionic resistance in carbon-based supercapacitors using electrochemical techniques and the analysis of the charge-storage dynamics

This study reports the in-situ characterization of nanosized carbon-based electrodes to identify and quantify the distributed capacitance and resistances verified in the time domain during the charge-storage process in aqueous-based symmetric coin cells. A theoretical model was proposed to represent the electrochemical response considering the presence of the so-called ‘inner’/internal and ‘outer’/external surface regions. The derivative analysis of the galvanostatic findings revealed the presence of two distinct voltage plateaux that were ascribed to the progressive assessment of the ‘outer’ and ‘inner’ surface regions by the ionic species. For the first time, it was demonstrated a connection between the heterogeneous surface nature of carbon electrodes and the charge-storage process in supercapacitors where different charge-storage dynamics regarding the migration of the ionic species can be identified due to the progressive transfer of ions from the ‘outer’ to the ‘inner’ surface regions as a function of the polarization time. The synthesized carbon materials were ex-situ characterized by scanning electron microscopy, Raman, and X-ray photoelectron spectroscopies. Specifically, the surface-modified MWCNTs allowed us to focus on a fundamental approach for studying the overall capacitance characteristics of nanostructured carbon-based electrodes. Thus, the charge-storage mechanism in the time domain and the individual contribution of the pseudocapacitance in the frequency domain were studied to clarify the real electrochemical behavior exhibited by porous carbon-based electrode materials.

Civility as Political Love: Likemindedness in a Time of Polarisation

Civility as Political Love: Likemindedness in a Time of Polarisation

Polarization Effect of Road Piezoelectric Energy Harvester under On-Site Road Conditions

Road piezoelectric energy harvesting based on the piezoelectric effect is a green energy utilization concept, which converts mechanical energy into electrical energy. Because of favorable properties such as low carbon significance, this technology caters to widespread applications. The major limitation of this concept is the fatigue degradation of piezoelectric transducers under long-term traffic loads, which subsequently reduces the energy conversion efficiency. Moreover replacing piezoelectric harvesters through road surface reconstruction will incur high costs and damage the integrity of road surface. With regard to the aforementioned factors, this study presents a polarization method for on-site road conditions from the perspective of the recovery and maximizing the piezoelectric energy harvester. First, the polarization of piezoelectric layer under simulated on-site road conditions was tested in a laboratory. The test results show that better transducer repolarization effect is observed when the polarization temperature is greater than 120 °C, the polarization time is less than 30 min, the polarization voltage is 2 kV/mm (greater than 1.2 kV/mm), and the d33 reaches 314 pC/N. Then, for an excitation frequency of 10 Hz and a test displacement of 1 mm, the piezoelectric harvester unit, which is based on the polarization method for on-site conditions, is used for piezoelectric performance test. The maximum output voltage of the polarized piezoelectric energy harvester is 10.47 V, which is 81.79% that of the initial polarization harvester in the indoor environment. The study proposes a polarization system under on-site conditions for road piezoelectric energy harvester and its equipment construction method, along with the future recycling processing applications after the road piezoelectric energy harvester reached the service life of the road.