Unambiguous Signal Research Articles

Effects of local motion ambiguity on perceptual confidence

Perceptual confidence refers to an observer’s judgment about his/her own performance in a perceptual task. It has been found to correlate with task performance in general, and is believed to be independent of stimulus features. However, certain stimulus feature could induce a subjective sense of uncertainty, which could potentially influence confidence judgments beyond task performance. The present study aimed at assessing the effects of the ambiguity of local motion signals on perceptual confidence on a global-motion task. The stimulus was a multiple-aperture array consisting of 188 randomly-oriented elements. Each element was either a Gabor, which is ambiguous in signaling a global motion direction, or an orthogonal plaid, which consists of an unambiguous local motion signal. In each trial, participants discriminated the global motion direction on a Gabor pattern and a plaid pattern, one after another. Then, they performed a two-interval, forced-choice confidence task by choosing which of the two perceptual responses they were more confident in being correct. Perceptual task performance was controlled by varying coherence, defined as the proportion of elements signaling a coherent global motion (leftward or rightward). A range of differences in coherence between Gabors and plaids was tested to create differences in perceptual task performance between the two types of stimuli. This allowed us to measure bias in confidence choices by fitting a psychometric function for confidence choices across differences in performance between Gabors and plaids. We found that the point of subjective equality (PSE) for confidence choice tended to favor better perceptual performance for Gabors. In other words, observers chose plaids more often than Gabors when task performance was matched between the two patterns. This suggests that, at the same level of objective task performance, ambiguous local motion signals are perceived to be more uncertain than unambiguous ones.

Paired Li/Ca and δ18O peaks in bivalve shells from the Gulf of Panama mark seasonal coastal upwelling

Paired lithium-to-calcium (Li/Cashell) and oxygen isotope (δ18Oshell) ratios were measured in four aragonitic Megapitaria aurantiaca bivalve shells from the tropical Eastern Pacific and evaluated with respect to their linkage to seasonal coastal upwelling. The Li/Cashell and δ18Oshell of two specimens from the upwelling-dominated Gulf of Panama are positively correlated and consistently reveal large seasonal variations of up to ~300 μmol/mol and ~3‰, respectively. The Li/Cashell and δ18Oshell of two shells from the adjacent non-upwelling Gulf of Chiriquí are not correlated and show a reduced seasonal variability rarely exceeding 20 μmol/mol and ~1.0‰, respectively. In some M. aurantiaca specimens the Li/Cashell shows a weak positive correlation with growth increment width, indicating that physiological growth rate effects might in part control the ‘background’ Li/Cashell. Unambiguous seasonal δ18Oshell signals, used for a precise chronology for a live-collected specimen from the Gulf of Panama, imply that distinct parallel peaks in Li/Cashell and δ18Oshell mark the cold and highly productive coastal upwelling season during February to April. A comparison with environmental data reveals a negative correlation between Li/Cashell and water temperature, and a strong positive correlation between Li/Cashell and chlorophyll a in the Gulf of Panama. While a causal link between Li/Cashell and temperature remains uncertain, we argue that Li/Cashell peaks in M. aurantiaca are consistent with the concept of an incorporation of additional Li provided by diatom-dominated phytoplankton blooms during coastal upwelling. Our findings suggest that Li/Cashell in M. aurantiaca may serve as a new proxy for seasonal coastal upwelling, the potential of which should be tested for other mollusk species and upwelling regions.

Tackling Anticompetitive Parallel Conduct under Personalized Pricing

This article investigates under what circumstances parallel conduct under personalized pricing is anticompetitive and whether it is within the scope of competition law, depending on which dimension of consumer preference heterogeneity is targeted by rival firms. Whilst enforcement against the use of personalized pricing based on consumers willingness to pay, and the lack thereof with respect to brand preferences, is problematic due to the inherent ambiguity at the inferential phase; the exploitative use of personalized pricing based on heterogeneous levels of search costs might be beyond the reach of competition because its sustainability is not underpinned by a collusive agreement. In contrast, evidence that firms are obstructing consumers use of third-party price aggregators may provide an unambiguous signal that they are colluding to obfuscate prices.

Unambiguous signal reconstruction for GEO‐LEO bistatic SAR with azimuth multichannel

Spaceborne bistatic multichannel synthetic aperture radar (MC-SAR) system employed inclined geosynchronous Earth orbit (GEO) transmitter and low-Earth-orbit (LEO) receiver can provide fine spatial resolution and a vast area of surveillance, which presents great potentials for future Earth observation. Nevertheless, owing to special geometry and big differences of orbital characteristics, the conventional effective phase centre (EPC) operation for unambiguous SAR signal reconstruction cannot be directly used. To address the issue, starting from geometry model of GEO-LEO bistatic MC-SAR, the new effective positions of the receiving channels are obtained. Then, the time-variant characteristics of residual phase error after the presented EPC processing is analysed. Finally, the method of reconstructing unambiguous SAR signal is presented. Simulation results show the validity of the proposed method, which can efficiently reconstruct the unambiguous signal for GEO-LEO bistatic SAR.

Sub-threshold Binary Neutron Star Search in Advanced LIGO’s First Observing Run

Abstract We present a search for gravitational waves from double neutron star binaries inspirals in Advanced Laser Interferometer Gravitational-Wave Observatory’s (LIGO’s) first observing run. The search considers a narrow range of binary chirp masses motivated by the population of known double neutron-star binaries in the nearby universe. This search differs from previously published results by providing the most sensitive published survey of neutron stars in Advanced LIGO’s first observing run within this narrow mass range, and also including times when only one of the two LIGO detectors was in operation in the analysis. The search was sensitive to binary neutron star (BNS) inspirals to an average distance of ∼85 Mpc over 93.2 days. We do not identify any unambiguous gravitational wave signals in our sample of 103 sub-threshold candidates with false-alarm rates of less than one per day. However, given the expected BNS merger rate of , we expect gravitational-wave events within our candidate list. This suggests the possibility that one or more of these candidates is in fact a BNS merger. Although the contamination fraction in our candidate list is ∼99%, it might be possible to correlate these events with other messengers to identify a potential multi-messenger signal. We provide an online candidate list with the times and sky locations for all events in order to enable multi-messenger searches.

A New Azimuth Ambiguity Suppression Algorithm for Surface Current Measurement in Coastal Waters and Rivers With Along-track InSAR

We present a new algorithm for suppressing azimuth ambiguities when measuring surface currents with an along-track interferometric (ATI) synthetic aperture radar in heterogeneous scenes, such as coastal waters or rivers. The key of the proposed algorithm involves a careful analysis of a parameter called the eigenvalue spectrum entropy (EVSE), which is defined as the entropy of the eigenvalue spectrum of the ATI covariance matrix computed in the Doppler domain. The physical meaning of EVSE is that it serves as a descriptor for the degree to which an unambiguous signal component and an ambiguous one are mixed. With the help of EVSE, azimuth ambiguities can be suppressed. Simulation results demonstrate that as compared with the conventional ATI method without azimuth ambiguity suppression, the proposed algorithm allows for a pronounced improvement in the current measuring accuracy. Other advantages of the proposed algorithm lie in the fact that it is not only adaptive, due to its ability to automatically capture the useful Doppler band whose width and position may both vary for different radar and scene parameters, but it also needs a minimal number of user inputs, making it a quite attractive algorithm for routine implementation.

Randomization of Pulse Phases for Unambiguous and Robust Quantum Sensing.

We develop theoretically and demonstrate experimentally a universal dynamical decoupling method for robust quantum sensing with unambiguous signal identification. Our method uses randomization of control pulses to simultaneously suppress two types of errors in the measured spectra that would otherwise lead to false signal identification. These are spurious responses due to finite-width π pulses, as well as signal distortion caused by π pulse imperfections. For the cases of nanoscale nuclear-spin sensing and ac magnetometry, we benchmark the performance of the protocol with a single nitrogen vacancy center in diamond against widely used nonrandomized pulse sequences. Our method is general and can be combined with existing multipulse quantum sensing sequences to enhance their performance.

Applications of Field-reversal and Angle-dependent XMCD Techniques to Mn-based Diluted Magnetic Materials

Recent progress of the soft X-ray magnetic circular dichroism (XMCD) techniques and relevant applications at beamline 4B7B in Beijing Synchrotron Radiation Facility are reported here. The key progress of the XMCD techniques include i) improvements in the accuracy and sensitivity of XMCD measurements by fast-reversing magnetic field with electromagnet, and ii) establishment an angle-dependent experimental method for obtaining the magnetic anisotropy information. These techniques have been applied to investigate the interface ferromagnetism and magnetic anisotropy of two Mn-based materials, i.e. Fe/(Ga,Mn)As and La2/3Sr1/3MnO3/SrTiO3 bilayer heterostructures. An enhanced XMCD signal has been observed at the Fe L2,3-edges whereas a relative small but unambiguous Mn XMCD signal with opposite sign has been detected which indicates an antiferromagnetic coupling at Fe/(Ga,Mn)As interfaces. A comparative study of the stoichiometric and nonstoichiometric La2/3Sr1/3MnO3/SrTiO3 bilayers clearly demonstrates that the oxygen vacancies degrade the magnetic properties of the perovskite manganese oxide film. These achievements benefit from the established field-reversal and angle-dependent XMCD techniques, which will make it possible to extend the research field of our devices from ferromagnetic to paramagnetic or diluted magnetic semiconductor system.

The eye of Gaia on globular clusters kinematics: internal rotation

We derived the three-dimensional velocities of individual stars in a sample of 62 Galactic globular clusters using proper motions from the second data release of the Gaia mission together with the most comprehensive set of line-of-sight velocities with the aim of investigating the rotation pattern of these stellar systems. We detect the unambiguous signal of rotation in 15 clusters at amplitudes which are well above the level of random and systematic errors. For these clusters, we derived the position and inclination angle of the rotation axis with respect to the line of sight and the overall contribution of rotation to the total kinetic energy budget. The rotation strengths are weakly correlated with the half-mass radius, the relaxation time and anticorrelated with the destruction rate, while no significant alignment of the rotation axes with the orbital poles has been observed. This evidence points toward a primordial origin of the systemic rotation in these stellar systems.

Insights on Hydrothermal‐Magmatic Interactions and Eruptive Processes at Poás Volcano (Costa Rica) From High‐Frequency Gas Monitoring and Drone Measurements

AbstractIdentification of unambiguous signals of volcanic unrest is crucial in hazard assessment. Processes leading to phreatic and phreatomagmatic eruptions remain poorly understood, inhibiting effective eruption forecasting. Our 5‐year gas record from Poás volcano, combined with geophysical data, reveals systematic behavior associated with hydrothermal‐magmatic eruptions. Three eruptive episodes are covered, each with distinct geochemical and geophysical characteristics. Periods with larger eruptions tend to be associated with stronger excursions in monitoring data, particularly in SO2/CO2 and SO2 flux. The explosive 2017 phreatomagmatic eruption was the largest eruption at Poás since 1953 and was preceded by dramatic changes in gas and geophysical parameters. The use of drones played a crucial role in gas monitoring during this eruptive period. Hydrothermal sealing and volatile accumulation, followed by top‐down reactivation of a shallow previously emplaced magma body upon seal failure, are proposed as important processes leading to and contributing to the explosivity of the 2017 eruption.

Empagliflozin Improves Diastolic Function in a Nondiabetic Rodent Model of Heart Failure With Preserved Ejection Fraction

Recent studies send an unambiguous signal that the class of agents known as sodium-glucose-linked co-transporter-2inhibitors (SGLT2i) prevent heart failure hospitalization in patients with type 2 diabetes. However, the mechanisms remain unclear. Herein the authors utilize a rodent model of heart failure with preserved ejection fraction (HFpEF), and demonstrate that treatment with the SGLT2i empagliflozin, reduces left ventricular mass, improving both wall stress and diastolic function. These findings extend the observation that the main mechanism of action of empagliflozin involves improved hemodynamics (i.e., reduction in preload and afterload) and provide a rationale for upcoming trials in patients with HFpEF irrespective of glycemic status.

A Channel Calibration Algorithm Based on Isolated Scatterers for Multi-Channel HRWS-SAR

Multi-channel receiving technique has been proved to be a promising approach for synthetic aperture radar (SAR) to achieve simultaneous high-resolution and wide-swath (HRWS) imaging. With the support of digital beamforming (DBF) technique, ambiguity-free signal can be reconstructed from the Doppler aliased data received by along-track channels with high fidelity. However, in practice, a key factor that affects the precision of spectrum reconstruction and deteriorates the quality of final image is the inevitable mismatch between receiving channels. Thus, channel calibration is recognized as a crucial step prior to DBF. In this paper, we propose a novel channel calibration algorithm for multi-channel HRWS-SAR system. Instead of using signal subspace projection or other matrix decomposition methods adopted in most of the existing HRWS-SAR channel calibration algorithms, it tries to find ambiguity-free “sample signal” to be used in the estimation of channel error directly from the original Doppler ambiguous data. We demonstrate that, by applying sub-aperture operation to the original data, unambiguous multi-channel signal corresponding to isolated ground scatterers can be extracted, and thereby can be utilized to accurately estimate and calibrate the azimuth-variant channel mismatch. Experimental results from a four-channel and a three-channel airborne SAR systems are employed to validate the effectiveness and robustness of the proposed algorithm in practical processing.

A Complete and Unambiguous 1H and 13C NMR Signals Assignment of para- Naphthoquinones, ortho- and para-Furanonaphthoquinones

A complete and unambiguous assignment of 1H and 13C nuclear magnetic resonance (NMR) signals of 29 naphthoquinones is reported on the basis of one- and two-dimensional NMR techniques (1H, 13C, 1H-1H correlated spectroscopy (COSY) and 1H-13C heteronuclear multiple-bond correlation (HMBC)). This is the first report distinguishing data between para-naphthoquinones, ortho- and para-furanonaphthoquinones isomers.

Lattice Evidence for Bound Heavy Tetraquarks

We investigate the possibility of qq'$ \bar {Q}\bar {Q}' $ tetraquark bound states using nf = 2 + 1 lattice QCD with pion masses ≃ 164, 299 and 415 MeV. Two types of lattice interpolating operator are chosen, reflecting first diquarkantidiquark and second meson-meson structure. Performing variational analysis using these operators and their mixings, we determine the ground and first excited states from the lattice correlators. Using non-relativistic QCD to simulate the bottom quarks and the Tsukuba formulation of relativistic heavy quarks for charm quarks, we study the ud$ \bar {b}\bar {b} $, ℓs$ \bar {b}\bar {b} $ as well as ud$ \bar {c}\bar {b} $, channels with ℓ= u, d. In the case of the ud$ \bar {b}\bar {b} $ and ℓs$ \bar {b}\bar {b} $ channels unambiguous signals for JP=1+ tetraquarks are found with binding energies 189(10) and 98(7) MeV below the corresponding free two-meson thresholds at the physical point. These tetraquarks are therefore strong-interaction stable, implying they are stable under strong as well as electromagnetic interactions while they can decay weakly. So far these are the first exotic hadrons predicted to have this feature. Further evidence for binding is found in the ud$ \bar {c}\bar {b} $ channel, whereby the binding energy broadly straddles the electromagnetic stability threshold. Studying further the quark mass dependence we vary the heavy quark mass in ud$ \bar {Q}\bar {Q} $, ℓs$ \bar {Q}\bar {Q} $ as well as ud$ \bar {Q}\bar {b} $, ℓs$ \bar {Q}\bar {b} $ between roughly 0.7 and 6.3 times the bottom quark mass. The observed mass dependence of these four flavor channels closely follows a behaviour argued from phenomenological considerations of the heavy baryon spectrum.

Test of discrete symmetries with neutral kaons at KLOE-2

The KLOE-2 experiment at the INFN Laboratori Nazionali di Frascati (LNF) completed its data-taking at the e+e− DAΦNE collider, which is implementing an innovative collision scheme based on a crab-waist configuration, and achieving the integrated luminosity goal of more than 5 fb−1. KLOE-2 represents the continuation of KLOE with an upgraded detector and an extended physics program which includes neutral kaon interferometry and test of discrete symmetries among the main topics. Entangled neutral kaon pairs produced at DAΦNE are a unique tool to test discrete symmetries and quantum coherence at the utmost sensitivity, in particular strongly motivating the experimental searches of possible CPT violating effects, which would constitute an unambiguous signal of a New Physics framework. The status of the latest ongoing analyses on KLOE/KLOE-2 data using the most refined analyses tools will be presented and discussed: (i) search for CP violating KS→3π0 decay, (ii) measurement of the KS semileptonic charge asymmetry and tests of CP and CPT symmetry, (iii) test of Time reversal and CPT in transitions in ϕ→KSKL→πν, 3π0, (2π) decays.

A record of changes in the Gran Sasso groundwater before, during and after the 2016 Amatrice earthquake, central Italy

We performed continuous recordings (May 2015 – January 2017) of hydraulic pressure and electrical conductivity of groundwater in the 190 m-long horizontal S13 borehole drilled next to the deep underground laboratories of Gran Sasso (LNGS-INFN), located in the core of the Gran Sasso carbonate aquifer (central Italy) at a distance of about 39 km south-eastward from the 24 August 2016 Amatrice earthquake (6.0 Mw) epicenter. Using a 3-channel, 24-bit ADC we achieved a sampling rate of groundwater physical properties up to 50 Hz for each channel. We focused on the analysis of data recorded before, during and after the Amatrice earthquake, describing and discussing in detail the evidence for significant hydraulic pressure and electrical conductivity anomalies recorded before the main shock. We identified unambiguous signals in the hydraulic pressure data starting on 19 August, i.e. five days before the 24 August mainshock. A more careful analysis allowed us to detect the inception of a weak change up to 40 days before the Amatrice earthquake and a significant variation in the electrical conductivity data about 60 days before. The data revealed highly dynamic aquifer behaviour associated with the uprising of geogas probably related to the preparation stage of the Amatrice earthquake.

Eolianite Grain Size Distributions as a Proxy for Large Changes in Planetary Atmospheric Density

AbstractAtmospheres are dynamic over geologic timescales, making large changes in planetary air density possible. For the Earth, geological proxies suggest that air density in the Neoarchean was similar to or lower than today. This air density variation possibly affected eolian dune grain sizes by controlling the trajectories of grains though the air. Balancing the fall velocity and threshold friction velocity, a metric separating saltation and suspension transport, suggests that a lower air density could increase the mean grain size of dunes because decreased air drag extends the size range of grains in modified saltation and incipient suspension regimes. Consequently, the dune‐forming sand left behind in pure saltation, the dominant dune‐forming transport mode, could have coarser grains. We analyzed size distributions of two eolianites from 2.64 and 1.5 Ga (billion years ago) for deviations from modern sand dunes emplaced at sea level, which globally exhibit similar mean grain sizes. Both aeolianites have mean grain sizes within one standard deviation of the modern mean and are not statistically separable at 95% confidence. Overall, this suggests that while air density is important in eolian physics, a factor of 2 to 4 change in density is insufficient to produce an unambiguous grain size signal. This suggests that while eolian dune grain sizes have not significantly changed over the range of Earth's atmospheric conditions, they could be useful when investigating the order of magnitude changes thought to have occurred on Mars.

코사인 BOC 신호를 위한 비모호 상관함수 기반의 신호 추적 기법

코사인 BOC 신호를 위한 비모호 상관함수 기반의 신호 추적 기법

Positive selection on schizophrenia-associated ST8SIA2 gene in post-glacial Asia.

A number of loci are associated with highly heritable schizophrenia and the prevalence of this mental illness has had considerable negative fitness effects on human populations. Here we focused on one particular schizophrenia-associated gene that encodes a sialyltransferase (ST8SIA2) and is expressed preferentially in the brain with the level being largely determined by three SNPs in the promoter region. It is suggested that the expression level of the ST8SIA2 gene is a genetic determinant of schizophrenia risk, and we found that a geographically differentiated non-risk SNP type (CGC-type) has significantly reduced promoter activity. A newly developed method for detecting ongoing positive selection was applied to the ST8SIA2 genomic region with the identification of an unambiguous sweep signal in a rather restricted region of 18 kb length surrounding the promoter. We also found that while the CGC-type emerged in anatomically modern humans in Africa over 100 thousand years ago, it has increased its frequency in Asia only during the past 20–30 thousand years. These findings support that the positive selection is driven by psychosocial stress due to changing social environments since around the last glacial maximum, and raise a possibility that schizophrenia extensively emerged during the Upper Paleolithic and Neolithic era.

Rareb-hadron decays as probe of new physics

The unexpected absence of unambiguous signals of New Physics (NP) at the TeV scale at the Large Hadron Collider (LHC) puts today flavor physics at the forefront. In particular, rare decays of b-hadrons represent a unique probe to challenge the Standard Model (SM) paradigm and test models of NP at a scale much higher than that accessible by direct searches. This article reviews the status of the field.