Detection Of New Events Research Articles

Exploiting Signal Coherence to Simultaneously Detect and Locate Earthquakes

Abstract This study introduces an earthquake detection and location technique that exploits the spatial coherence of the seismic wavefield. The method leverages the signal coherence across clusters of seismic stations to generate characteristic functions that are backprojected (migrated) to detect and locate seismic events. The effectiveness of the technique is assessed using a limited set of stations from the Oklahoma wavefield experiment, with minimal tuning of processing parameters. The technique is then applied to one day of continuous data, leading to the detection of new seismic events compared with an analyst-based catalog. Noteworthy advantages of this method include its independence from prior information or assumptions (such as template waveform) and its ability to operate effectively with a network design for which seismometers are deployed in a relatively small number of clusters rather than distributed throughout a region.

SAR Coherence in Detecting Fluvial Sediment Transport Events in Arid Environments

Coherence change detection (CCD) is a remote sensing technique used to map phenomena that, under certain conditions, can be directly related to changes in Interferometric SAR (InSAR) coherence. Mapping the areas affected by sediment transport events in arid environments is one of the most common applications of CCD. However, the reliability of these maps remains an unsolved issue. This paper focuses on verifying that InSAR coherence is indeed able to detect all the fluvial sediment transport events that have actually mobilised sediments in arid environments by building a classification model and validating its results. The proposed methodology is tested in three study areas in Salar de Atacama, Chile, using three years of Sentinel data plus a fourth year for validation, and meteorological records of rainfall, the relative humidity of the air and snow cover. The results prove that InSAR coherence can be used to remotely detect sediment transport events related to flash floods in arid environments, that it might have a greater detection ability than meteorological records and that the perpendicular baseline does have a relevant effect on the InSAR coherence that needs to be considered. All these findings will increase the reliability of maps based on InSAR coherence. In addition, the proposed method will allow focusing the mapping tasks only on the relevant dates and, once calibrated, the classification model will enable the automatised remote detection of new events.

Neural auditory contrast enhancement in humans

The perception of sensory events can be enhanced or suppressed by the surrounding spatial and temporal context in ways that facilitate the detection of novel objects and contribute to the perceptual constancy of those objects under variable conditions. In the auditory system, the phenomenon known as auditory enhancement reflects a general principle of contrast enhancement, in which a target sound embedded within a background sound becomes perceptually more salient if the background is presented first by itself. This effect is highly robust, producing an effective enhancement of the target of up to 25 dB (more than two orders of magnitude in intensity), depending on the task. Despite the importance of the effect, neural correlates of auditory contrast enhancement have yet to be identified in humans. Here, we used the auditory steady-state response to probe the neural representation of a target sound under conditions of enhancement. The probe was simultaneously modulated in amplitude with two modulation frequencies to distinguish cortical from subcortical responses. We found robust correlates for neural enhancement in the auditory cortical, but not subcortical, responses. Our findings provide empirical support for a previously unverified theory of auditory enhancement based on neural adaptation of inhibition and point to approaches for improving sensory prostheses for hearing loss, such as hearing aids and cochlear implants.

Quasi anomalous knowledge: searching for new physics with embedded knowledge

Discoveries of new phenomena often involve a dedicated search for a hypothetical physics signature. Recently, novel deep learning techniques have emerged for anomaly detection in the absence of a signal prior. However, by ignoring signal priors, the sensitivity of these approaches is significantly reduced. We present a new strategy dubbed Quasi Anomalous Knowledge (QUAK), whereby we introduce alternative signal priors that capture some of the salient features of new physics signatures, allowing for the recovery of sensitivity even when the alternative signal is incorrect. This approach can be applied to a broad range of physics models and neural network architectures. In this paper, we apply QUAK to anomaly detection of new physics events at the CERN Large Hadron Collider utilizing variational autoencoders with normalizing flow.

New binary black hole mergers in the second observing run of Advanced LIGO and Advanced Virgo

We report the detection of new binary black hole merger events in the publicly available data from the second observing run of advanced LIGO and advanced Virgo (O2). The mergers were discovered using the new search pipeline described in Venumadhav et al. [Phys. Rev. D 100, 023011 (2019)], and are above the detection thresholds as defined in Abbott et al. (LIGO Scientific and Virgo Collaborations) [Phys. Rev. X 9, 031040 (2019).] Three of the mergers (GW170121, GW170304, GW170727) have inferred probabilities of being of astrophysical origin $p_{\rm astro} > 0.98$. The remaining three (GW170425, GW170202, GW170403) are less certain, with $p_{\rm astro}$ ranging from 0.5 to 0.8. The newly found mergers largely share the statistical properties of previously reported events, with the exception of GW170403, the least secure event, which has a highly negative effective spin parameter $\chi_{\rm eff}$ . The most secure new event, GW170121 ($p_{\rm astro} > 0.99$), is also notable due to its inferred negative value of $\chi_{\rm eff}$, which is inconsistent with being positive at the ~95.8% confidence level. The new mergers nearly double the sample of gravitational wave events reported from O2, and present a substantial opportunity to explore the statistics of the binary black hole population in the Universe. The number of detected events is not surprising since we estimate that the detection volume of our pipeline may be larger than that of other pipelines by as much as a factor of two (with significant uncertainties in the estimate). The increase in volume is larger when the constituent detectors of the network have very different sensitivities, as is likely to be the case in current and future runs.

Time from incident primary cancer until recurrence or second primary cancer: Risk factors and impact in general practice.

Specialised follow-up care after cancer treatment is changing towards increased involvement of general practice. To ensure timely detection of new cancer events, knowledge is warranted on the timing of cancer recurrence (CR) and second primary cancer (SPC), including risk factors for CR. This population-based register study included 67,092 patients diagnosed with malignant melanoma, bladder, lung, ovarian, endometrial, colorectal and breast cancer in Denmark in 2008-2016. The time from primary cancer to CR or SPC and risk factors for prolonged time to CR were analysed and stratified on sex and primary cancer type. Cancer recurrence proportions ranged from 6% to 35%. The risk of CR increased profoundly within the first 3years and then levelled off, except for breast cancer. A total of 3%-6% of patients had SPC, with monotonously increasing cumulative incidence proportions. Besides primary tumour characteristics, lower educational level, living alone and comorbidity were associated with earlier CR. For example, in female malignant melanoma, HRs and 95% confidence intervals were 0.47 (0.37-0.61) for high educational level, 1.40 (1.16-1.68) for living alone and 2.38 (1.53-3.70) for high comorbidity. The results may inform stratified risk assessment in decision of frequency, location and duration of post-cancer follow-up care.

Simulation of quasi spherical gravitational waves in the characteristic formulation

Introduction :A review is made of gravitational waves, their simulation and the methods used for their definitive detection in 2015. A comparison of electromagnetic waves with gravitational waves and the main technological efforts made over decades for their detection is presented. Objective:is to detect OG from massive black holes and galactic and extragalactic binary stars in a frequency range of 10-4 to 10-1 Hz. Materials and methods: Numerical methods used in its simulation are specified, emphasizing computational techniques used in recent years. Results:The boundary is placed at x = 2/3 and the parameters are used for the simulations shown in figures 3 and 4: number of points of the angular mesh Nq = Np = Nξ = 45, and for the radial mesh Nx = 100 , A = 10-3, Ra = 4, Rb = 7. Discussion:The simulations were carried out with a code programmed in FORTRAN 90 and run under the LINUX free software platform. The figures were generated with the Dx plotter under LINUX environment, allowed to evaluate the respective equations and give a satisfactory answer to the proposed objectives. Conclusions:it was possible to conclude that the detection of gravitational waves is possible, however it is necessary to improve the sensitivity, which will allow the detection of new events collecting information about sources three times more distant, and increasing the probability of detection.

Enhanced deviant responses in patterned relative to random sound sequences

The brain draws on knowledge of statistical structure in the environment to facilitate detection of new events. Understanding the nature of this representation is a key challenge in sensory neuroscience. Specifically, it is unknown whether real-time perception of rapidly-unfolding sensory signals is driven by a coarse or detailed representation of the proximal stimulus history. We recorded electroencephalography brain responses to frequency outliers in regularly-patterned (REG) versus random (RAND) tone-pip sequences which were generated anew on each trial. REG and RAND sequences were matched in frequency content and span, only differing in the specific order of the tone-pips. Stimuli were very rapid, limiting conscious reasoning in favour of automatic processing of regularity. Listeners were naïve and performed an incidental visual task. Outliers within REG evoked a larger response than matched outliers in RAND. These effects arose rapidly (within 80 msec) and were underpinned by distinct sources from those classically associated with frequency-based deviance detection. These findings are consistent with the notion that the brain continually maintains a detailed representation of ongoing sensory input and that this representation shapes the processing of incoming information. Predominantly auditory-cortical sources code for frequency deviance whilst frontal sources are associated with tracking more complex sequence structure.

Auditory enhancement and the role of spectral resolution in normal-hearing listeners and cochlear-implant users.

Detection of a target tone in a simultaneous multi-tone masker can be improved by preceding the stimulus with the masker alone. The mechanisms underlying this auditory enhancement effect may enable the efficient detection of new acoustic events and may help to produce perceptual constancy under varying acoustic conditions. Previous work in cochlear-implant (CI) users has suggested reduced or absent enhancement, due perhaps to poor spatial resolution in the cochlea. This study used a supra-threshold enhancement paradigm that in normal-hearing listeners results in large enhancement effects, exceeding 20 dB. Results from vocoder simulations using normal-hearing listeners showed that near-normal enhancement was observed if the simulated spread of excitation was limited to spectral slopes no shallower than 24 dB/oct. No significant enhancement was observed on average in CI users with their clinical monopolar stimulation strategy. The variability in enhancement between CI users, and between electrodes in a single CI user, could not be explained by the spread of excitation, as estimated from auditory nerve evoked potentials. Enhancement remained small, but did reach statistical significance, under the narrower partial-tripolar stimulation strategy. The results suggest that enhancement may be at least partially restored by improvements in the spatial resolution of current CIs.

Wearable expert system development: definitions, models and challenges for the future

PurposeA wearable expert system (WES) is an expert system designed and implemented to obtain input from and give outputs to wearable devices. Among its distinguishing features are the direct cooperation between domain experts and users, and the interaction with a knowledge maintenance system devoted to dynamically update the knowledge base taking care of the evolving scenario. The paper aims to discuss these issues.Design/methodology/approachThe WES development method is based on the Knowledge Acquisition Framework based on Knowledge Artifact (KAFKA) framework. KAFKA employs multiple knowledge artifacts, each devoted to the acquisition and management of a specific kind of knowledge. The KAFKA framework is introduced from both the conceptual and computational points of view. An example is given which demonstrates the interaction, within this framework, of taxonomies, Bayesian networks and rule-based systems. An experimental assessment of the framework usability is also given.FindingsThe most interesting characteristic of WESs is their capability to evolve over time, due both to the measurement of new values for input variables and to the detection of new input events, that can be used to modify, extend and maintain knowledge bases and to represent domains characterized by variability over time.Originality/valueWES is a new and challenging concept, dealing with the possibility for a user to develop his/her own decision support systems and update them according to new events when they arise from the environment. The system fully supports domain experts and users with no particular skills in knowledge engineering methodologies, to create, maintain and exploit their expert systems, everywhere and when necessary.

TRANSIENT EVENTS IN ARCHIVAL VERY LARGE ARRAY OBSERVATIONS OF THE GALACTIC CENTER

ABSTRACT The Galactic center has some of the highest stellar densities in the Galaxy and a range of interstellar scattering properties, which may aid in the detection of new radio-selected transient events. Here, we describe a search for radio transients in the Galactic center, using over 200 hr of archival data from the Very Large Array at 5 and 8.4 GHz. Every observation of Sgr A* from 1985 to 2005 has been searched using an automated processing and detection pipeline sensitive to transients with timescales between 30 s and 5 minutes with a typical detection threshold of ∼100 mJy. Eight possible candidates pass tests to filter false-positives from radio-frequency interference, calibration errors, and imaging artifacts. Two events are identified as promising candidates based on the smoothness of their light curves. Despite the high quality of their light curves, these detections remain suspect due to evidence of incomplete subtraction of the complex structure in the Galactic center, and apparent contingency of one detection on reduction routines. Events of this intensity (∼100 mJy) and duration (∼100 s) are not obviously associated with known astrophysical sources, and no counterparts are found in data at other wavelengths. We consider potential sources, including Galactic center pulsars, dwarf stars, sources like GCRT J1745−3009, and bursts from X-ray binaries. None can fully explain the observed transients, suggesting either a new astrophysical source or a subtle imaging artifact. More sensitive multiwavelength studies are necessary to characterize these events, which, if real, occur with a rate of in the Galactic center.

New perspectives on the measurement and time course of auditory enhancement.

A target sound can become more audible and may "pop out" from a simultaneously presented masker if the masker is presented first by itself, as a precursor. This phenomenon, known as auditory enhancement, may reflect the general perceptual principle of contrast enhancement, which facilitates adaptation to ongoing acoustic conditions and the detection of new events. Little is known about the mechanisms underlying enhancement, and potential confounding factors have made the size of the effect and its time course a point of contention. Here we measured enhancement as a function of precursor duration and delay between precursor offset and target onset, using 2 single-interval pitch comparison tasks, which involve either same-different or up-down judgments, to avoid the potential confounds of earlier studies. Although these 2 tasks elicit different levels of performance and may reflect different underlying mechanisms, they produced similar amounts of enhancement. The effect decreased with decreasing precursor duration, but remained present for precursors as short as 62.5 ms, and decreased with increasing gap between the precursor and target, but remained measurable 1 s after the precursor. Additional conditions, examining the effect of precursor/masker similarity and the possible role of grouping and cueing, suggest multiple sources of auditory enhancement.

Нейронные механизмы нарушений ориентировки внимания у детей с расстройством аутистического спектра

Detection of new events occurring outside the focus of attention is fundamental to adaptive functioning and is most critical when attention is focused elsewhere. The unattended novel sensory events may demand further analysis according to their task relevance and may appear important for survival. Behavioral and physiological findings reviewed in this article imply that brains of many people with autism spectrum disorders (ASD) are, to a certain extent, impenetrable to such unattended but potentially salient changes in the immediate sensory environment. Here we reviewed neurophysiological studies investigating neural processing of salient (rare, novel or deviant) auditory stimuli in ASD. We put forward a hypothesis that atypical processing of deviance and novelty in a proportion of individuals with ASD may be grounded in the failure of nicotinic cholinergic arousal pathways to engage cortical mechanisms involved in detection of changes in the environment and appraisal of their novelty, if these changes occur beyond the currently attended sensory stream. Further studies linking neurophysiological findings with attention behavior and those searching for their neurochemical and genetic bases will help to understand causes of attention problems and sensory modulation difficulties in children with ASD and may prove helpful to direct early intervention

A role of the claustrum in auditory scene analysis by reflecting sensory change

The biological function of the claustrum remains speculative, despite many years of research. On the basis of its widespread connections it is often hypothesized that the claustrum may have an integrative function mainly reflecting objects rather than the details of sensory stimuli. Given the absence of a clear demonstration of any sensory integration in claustral neurons, however, we propose an alternative, data-driven, hypothesis: namely that the claustrum detects the occurrence of novel or salient sensory events. The detection of new events is critical for behavior and survival, as suddenly appearing objects may require rapid and coordinated reactions. Sounds are of particular relevance in this regard, and our conclusions are based on the analysis of neurons in the auditory zone of the primate claustrum. Specifically, we studied the responses to natural sounds, their preference to various sound categories, and to changes in the auditory scene. In a test for sound-category preference claustral neurons responded to but displayed a clear lack of selectivity between monkey vocalizations, other animal vocalizations or environmental sounds (Esnd). Claustral neurons were however able to detect target sounds embedded in a noisy background and their responses scaled with target signal to noise ratio (SNR). The single trial responses of individual neurons suggest that these neurons detected and reflected the occurrence of a change in the auditory scene. Given its widespread connectivity with sensory, motor and limbic structures the claustrum could play the essential role of identifying the occurrence of important sensory changes and notifying other brain areas—hence contributing to sensory awareness.

Extensive Leukoaraiosis Is Associated With High Early Risk of Recurrence After Ischemic Stroke

The integrity of white matter tracts connecting different parts of the brain is important for rapid compensation for the lost function from ischemic stroke. Impaired white matter reserve capacity secondary to leukoaraiosis may facilitate detection of new symptomatic ischemic events that would otherwise remain inconspicuous after an initial ischemic stroke. We sought to identify whether the extent of leukoaraiosis was a predictor of risk of early stroke recurrence. We used Cox regression analysis in consecutive patients with ischemic stroke to determine the relationship between leukoaraiosis burden and symptomatic stroke recurrence within 90 days. We graded total leukoaraiosis, periventricular leukoaraiosis, and subcortical leukoaraiosis using the Fazekas scale as mild (<2) and extensive (≥2) on fluid-attenuated inversion recovery images obtained within 72 hours of stroke onset in the hemisphere contralateral to acute stroke. There were 106 recurrent events in 2378 patients. The cumulative incidence of recurrence was 5.9% at 90 days. Kaplan-Meier estimate of recurrence-free survival rate was lower in patients with extensive leukoaraiosis (P=0.04) and extensive periventricular leukoaraiosis (P=0.02) but not in extensive subcortical leukoaraiosis (P=0.09). Multivariable Cox regression analysis revealed a hazard ratio of 1.50 (95% confidence interval, 1.00-2.25) for extensive leukoaraiosis, 1.67 (95% confidence interval, 1.11-2.51) for extensive periventricular leukoaraiosis, and 1.42 (95% confidence interval, 0.94-2.12) for extensive subcortical leukoaraiosis. The extent of leukoaraiosis independently predicts 90-day recurrent stroke risk after ischemic stroke. This suggests that leukoaraiosis may be used for risk stratification in ischemic stroke.

Improbability mapping: A metric for satellite-detection of submarine volcanic eruptions

Submarine volcanic eruptions can result in both real and apparent changes in marine algal communities, e.g., increases in phytoplankton biomass and/or growth rates that can cover thousands of square kilometers. Satellite ocean color monitoring detects these changes as increases in chlorophyll and particulate backscattering. Detailed, high resolution analysis is needed to separate the optical effects of volcanic products from the response of the marine algal community. It is possible to calculate an index, which maps the magnitude of improbable change (relative to long term average conditions) following known volcanic eruptions by using low resolution, initial estimates of chlorophyll and backscatter along with an archived history of satellite data. We apply multivariate probability analysis to changes in global satellite ocean chlorophyll and particulate backscatter data to create a new metric for observing apparent biological responses to submarine eruptions. Several examples are shown, illustrating the sensitivity of our improbability mapping index to known submarine volcanic events, yielding a potentially robust method for the detection of new events in remote locations.

Evidence of ongoing replication in a human immunodeficiency virus type 1 persistently infected cell line

Human immunodeficiency virus type 1 (HIV-1) persistently infected cell lines are characterized by the continuous viral production without cytopathic effect. However, it is not completely clear if this production is contributed only by viral transcription or also by new cycles of viral replication. We studied an HIV-1 persistently infected cell line, designated H61-D, providing evidence of new replication cycles as sustained by: (i) a decrease in viral production, measured by p24 protein, after treatment of the culture with 3'-azydo-3'-deoxythymydine; (ii) detection of new integration events in the course of cell culture, and (iii) finding of two-long-terminal repeat circles in the cells. H61-D cells were not infected by cell-free virus, but infection was possible by co-culture with another productive-infected cell line. In conclusion, ongoing viral replication is taking place in H61-D persistent cells and new infections are mediated by a cell-to-cell spread mechanism.

Activity evolution, outbursts, and splitting events of comet 73P/Schwassmann-Wachmann 3

Context. The split Jupiter family comet 73P/Schwassmann-Wachmann 3 was monitored between January 21 and May 25 2006, for 24 nights. Aims. The goals of the campaign were to characterize the two principal comet components (C and B) and the smaller component G during their approach to perihelion, and study differences and commonalities in their evolution to obtain insight into the nature of the nuclei (gas and dust). We aimed to assess the chemical homogeneity/heterogeneity of the different components, the presence of jets and other coma structures, the rotation axis, the long-term activity evolution, and the detection of new fragmentation events. Methods. Long-slit spectra and optical broadband images were acquired using the CAFOS instrument at the 2.2-m telescope at Calar Alto Observatory (CSIC-MPG). Data obtained in service mode consisted of spectra and Johnson R filter images. By observing for four nights close to perigee, the comet could be imaged in the Johnson UBVRI filters. When possible, we analyzed the radial profile of the dust brightness and we derived the dust and gas production rates, the dust reddening, and the N-S profiles of the CN, C2, and C3 column densities. The analysis of the morphological evolution of coma structures and the determination of the rotation axis is performed in a separate paper. Results. We found that components C and B behave differently during most of our observations. While component C did not show any sudden increase in dust productivity, as measured by Afρ, component B was characterized by a higher activity variation, exhibiting two outburst peaks and fragmentation events. Excluding outburst dates, component B always had lower dust productivity than component C. We also found differences in the behavior of the dust brightness radial profiles and in the dust colors. Differences in the dust colors are found also with respect to component G. In the spectral analysis, we found that both C and B components seem to be carbon-chain depleted, their compositions being almost the same. This indicates that the pre-split original intact nucleus probably had a homogenous composition. A two-dimensional color map of component B on May 13 shows relative color variations in the inner coma that can be interpreted qualitatively in terms of Mie theory as fragmentation of silicate dust particles emanating from the nucleus.

Practical implementation of a nontrivial evolution “unravelling” for a resonantly fluorescing atom

One of the consequences of the implementation of the so-called nontrivial “unravelling” of the resonance fluorescence of a two-level atom is considered. Namely, we consider the artificial re-aiming of the environment at the detection of a new set of events that are different from the photoemission to the components of a resonance fluorescence triplet. The atomic states obtained after the detection of new events are studied, and the element providing the maximum probability of the atom occurring in the excited state is found for the simplest unravelling class.

Some US Food and Drug Administration perspectives on data mining for pediatric safety Assessment

Background: The US Food and Drug Administration's (FDA's) large spontaneous reporting database contains >110,000 voluntary reports of adverse drug events (ADEs) observed during postmarketing pediatric practice and submitted to the FDA by manufacturers, health care providers, or consumers. These reports may provide evidence about known or unknown harm associated with single or combination drug treatments in pediatric patients. We recently implemented new Bayesian data mining tools to evaluate >2 million reports stored in this database to help systematically identify safety signals that appear with unexpectedly high frequency. Objective: The purpose of this paper was to describe the current status of the application of Bayesian data mining tools to screen pediatric reports of ADEs submitted spontaneously to the FDA. Methods: We applied DuMouchel's empirical Bayesian data mining algorithms to the FDA's spontaneous reporting database. These methods circumvent the lack of exposure denominators in passive surveillance data. The first method implemented, the Gamma-Poisson Shrinkage model (GPS) computer program, detects higher-than-expected associations between drugs and adverse events. The method currently being used, the updated GPS program implemented in a software program called MGPS, adjusts for the multiplicity of drugs and events per record in the data reported after October 1997 and generalizes to multiple combinations of drugs and events (eg, triples, quadruples) that occur together in reports with unexpectedly high frequency. MGPS also identifies how much these unusually frequent itemsets can be explained by pairwise associations. For this article, we used the MGPS program to analyze pairwise, higher-than-expected associations between drugs and adverse events in pediatric reports. Results: We illustrate the potential of the data mining techniques to improve the early detection and analysis of new adverse events involving unusually frequent drug-event pairs in pediatric reports and to verify the significance of known ADEs. Conclusions: New data mining techniques help skilled safety evaluators and epidemiologists at the FDA analyze reports of pediatric ADEs submitted to the FDA spontaneously. These tools are not intended to replace current pharmacovigilance techniques but to enhance them. In the near future, these techniques should facilitate our study of potential drug interactions, a serious problem for pediatric patients requiring complicated medication regimens.