Changes In Coherence Research Articles

APPLICATION OF U-NET CONVOLUTIONAL NEURAL NETWORK TO BUSHFIRE MONITORING IN AUSTRALIA WITH SENTINEL-1/-2 DATA

Abstract. This paper aims to define a pipeline architecture for near real-time identification of bushfire impact areas using Geoscience Australia Data Cube (AGDC). A series of catastrophic bushfires from late 2019 to early 2020 have captured international attention with their scale of devastation across four of the most populous states across Australia; New South Wales, Queensland, Victoria and South Australia. The extraction of burned areas using multispectral Sentinel-2 observations are straightforward when no cloud or haze obstruction are present. Without clear-sky observations, precisely locating the bushfire affected regions are difficult to achieve. Sentinel-1 C-band dual-polarized (VH/VV) Synthetic Aperture Radar (SAR) data is introduced to effectively elicit and analyse useful information based on backscattering coefficients, unaffected by adverse weather conditions and lack of sunlight. Burned vegetation results in significant volume scattering; co-/cross-polarised response decreases due to leafless trees, as well as coherence change over fire-disturbed areas; two sensors acquired images in a shortened revisit time over the same effected areas; all of which provided discriminative features for identifying burnt areas. Moreover, applying U-Net deep learning framework to train the recent and historical satellite data leads to an effective pre-trained segmentation model of burnt and non-burnt areas, enabling more timely emergency response, more efficient hazard reduction activities and evacuation planning during severe bushfire events. The advantages of this approach could have profound significance for a more robust, timely and accurate method of bushfire detection, utilising a scalable big data processing framework, to predict the bushfire footprint and fire spread model development.

High-fidelity vibrokinetic stimulation induces sustained changes in intercortical coherence during a cinematic experience

Objective. High-fidelity vibrokinetic (HFVK) technology is widely used to enhance the immersiveness of audiovisual (AV) entertainment experiences. However, despite evidence that HFVK technology does subjectively enhance AV immersion, the underlying mechanism has not been clarified. Neurophysiological studies could provide important evidence to illuminate this mechanism, thereby benefiting HFVK stimulus design, and facilitating expansion of HFVK technology. Approach. We conducted a between-subjects (VK, N = 11; Control, N = 9) exploratory study to measure the effect of HFVK stimulation through an HFVK seat on electroencephalographic cortical activity during an AV cinematic experience. Subjective appreciation of the experience was assessed and incorporated into statistical models exploring the effects of HFVK stimulation across cortical brain areas. We separately analyzed alpha-band (8–12 Hz) and theta-band (5–7 Hz) activities as indices of engagement and sensory processing, respectively. We also performed theta-band (5–7 Hz) coherence analyses using cortical seed areas identified from the theta activity analysis. Main results. The right fusiform gyrus, inferiotemporal gyrus, and supramarginal gyrus, known for emotion, AV-spatial, and vestibular processing, were identified as seeds from theta analyses. Coherence from these areas was uniformly enhanced in HFVK subjects in right motor areas, albeit predominantly in those who were appreciative. Meanwhile, compared to control subjects, HFVK subjects exhibited uniform interhemispheric decoherence with the left insula, which is important for self-processing. Significance. The results collectively point to sustained decoherence between sensory and self-processing as a possible mechanism for how HFVK increases immersion, and that coordination of emotional, spatial, and vestibular processing hubs with the motor system may be required for appreciation of the HFVK-enhanced experience. Overall, this study offers the first ever demonstration that HFVK stimulation has a real and sustained effect on brain activity during a cinematic experience.

Evaluation of the effects of integrative non-pharmacological interventions on the internal coherence and resilience of breast cancer patients.

In the breast cancer center at the Gemeinschaftskrankenhaus Havelhöhe (GKH), integrative strategies are implemented in the routine care of breast cancer patients. The aim of this breast cancer real-world study was to systematically evaluate changes in patients' internal coherence and resilience, associated with the use of non-pharmacological interventions (NPIs). This study included 231 primary breast cancer patients treated with standard oncological therapy and NPIs, which comprise art and movement therapies, nursing interventions, and educational components, and had answered the internal coherence scale (ICS) questionnaire at first diagnosis and 12months later. Data were collected from the Network Oncology clinical registry of the GKH, and effects of NPIs on ICS changes were analyzed with adjusted linear multivariable regression analyses, using the software R. Two hundred twenty breast cancer patients of all tumor stages were eligible for a total of 27 separate adjusted multivariable linear regression analyses. The NPIs elaborate consultations and life review (ECLR); nursing compresses, music therapy, and rhythmic massages were significantly associated with increases of about 2-point changes in inner resilience and coherence (p< 0.05). Furthermore, a significant association with an elevation of the thermo coherence was observed for the application of nursing compresses. The evaluation of real-world data carried out here shows that the application of the multimodal treatment concept can lead to an enhancement of the internal coherence and resilience in breast cancer patients. To improve the care of cancer patients, this multimodal program should be further expanded into routine clinical practices. Trial registration number DRKS00013335 on 27/11/2017 retrospectively registered.

Lagged Compound Occurrence of Droughts and Pluvials Globally Over the Past Seven Decades

AbstractThe drought‐pluvial seesaw—defined as the phenomenon of pluvials (wet spells) following droughts (dry spells)—magnifies the impact of individual pluvial and drought events yet has not been systematically evaluated, especially at the global scale. We apply an event coincidence analysis to explore the aggregated seesaw behavior based on land surface model simulations for the past seven decades (1950–2016). We find that globally, about 5.9% and 7.6% of the land surface have experienced statistically significant (p&lt;0.10) drought‐pluvial seesaw behavior during the boreal spring‐summer and fall‐winter, with an average 11.1% and 11.4% of all droughts being followed by pluvials in the following season, respectively. Although this global frequency pattern is modest and coherent changes cannot be detected at the subcontinental scale, local hot spots of drought‐pluvial seesaw have become more frequent than either droughts or pluvials alone in the last three decades, albeit with a small percentage of area coverage.

Effect of Acute Hypoxia on Cardiorespiratory Coherence in Male Runners.

Understanding the mechanisms of oxygen supply regulation, which involves the respiratory and cardiovascular systems, during human adaptation to intense physical activity, accompanied by hypoxemia, is important for the management of a training process. The objectives of this study were to investigate the cardiorespiratory coherence (CRC) changes in the low-frequency band in response to hypoxic exposure and to verify a dependence of these changes upon sports qualification level in athletes. Twenty male runners aged 17–25 years were exposed to acute normobaric hypoxia (10% O2) for 10 min. Respiration, gas exchange, and heart rate were measured at baseline, during hypoxia, and after the exposure. To evaluate cardiorespiratory coupling, squared coherence was calculated based on 5-s averaged time series of heart and respiratory rhythms. Based on sports qualification level achieved over 4 years after the experimental testing, athletes were retrospectively divided into two groups, one high level (HLG, n = 10) and the other middle level (MLG, n = 10). No differences in anthropometric traits were observed between the groups. In the pooled group, acute hypoxia significantly increased CRC at frequencies 0.030–0.045 Hz and 0.075 Hz. In response to hypoxia, oxygen consumption decreased in HLG, and carbon dioxide production and ventilation increased in MLG. At 0.070–0.080 Hz frequencies in hypoxia, the CRC in HLG was higher than in MLG. Thus, highly qualified athletes enhance intersystem integration in response to hypoxia. This finding can be a physiological sign for the prognosis of qualification level in runners.

Reward-related dynamical coupling between basolateral amygdala and nucleus accumbens.

Recognizing reward-related stimuli is crucial for survival. Neuronal projections from the basolateral amygdala (BLA) to the nucleus accumbens (NAc) play an important role in processing reward-related cues. Previous studies revealed synchronization between distant brain regions in reward-sensitive neurocircuits; however, whether the NAc synchronizes with the BLA is unknown. Here, we recorded local field potentials simultaneously from the BLA and NAc of rats during social preference tests and an appetitive conditioning test in which explicit stimuli were associated with food. BLA-NAc coherence in the theta band (5-8Hz) increased in response to food-associated cues. Meanwhile, the modulatory strength of theta-high gamma (50-110Hz) phase-amplitude cross-frequency coupling (PAC) in the NAc decreased. Importantly, both of these neuromodulations disappeared upon extinction. In contrast, both theta and gamma power oscillations in each region increased in the presence of social conspecifics or contexts associated with conspecifics, but coherence did not change. To potentially disrupt behavior and associated neural activity, a subgroup of rats was exposed prenatally to valproic acid (VPA), which has been shown to disrupt transcriptome and excitatory/inhibitory balance in the amygdala. VPA-exposed rats demonstrated impulsive-like behavior, but VPA did not affect BLA-NAc coherence. These findings reveal changes in BLA-NAc coherence in response to select reward-related stimuli (i.e., food-predictive cues); the differences between the tasks used here could shed light onto the functional nature of BLA-NAc coherence and are discussed.

Effect of superhydrophobicity on the flow past a circular cylinder in various flow regimes

The flow over a superhydrophobic and a smooth circular cylinder is investigated using particle image velocimetry-based experiments. The objective is to understand the effect of surface modification on the ensuing flow. The experiments are conducted over a wide range of Reynolds numbers, , thereby uncovering the effect of superhydrophobicity in various flow regimes of a cylinder wake. Superhydrophobicity is found to substantially affect the flow. An increased recirculation length is observed for the superhydrophobic cylinder in the steady regime. The onset of vortex shedding is delayed for the superhydrophobic cylinder. The superhydrophobic cylinder helps in an early rolling-up of vortices; therefore, the recirculation length reduces in unsteady regimes. The velocity deficit experienced by the superhydrophobic cylinder wake is comparatively less and the effect is more profound in the range 300–860. A maximum drag reduction of 15 % is observed at . The Reynolds shear stress and turbulent kinetic energy values are higher for the superhydrophobic cylinder in the unsteady regime. Also, the peaks of the turbulent wake parameters lie closer to the superhydrophobic cylinder compared to the smooth cylinder. The effect of superhydrophobicity on coherent structures is examined using proper orthogonal decomposition, and a considerable difference in the wake structure is noticed at . A larger number of coherent structures and change in vortex shedding pattern to are observed in the near wake of the superhydrophobic cylinder. The results of this study show that surface modification can reduce the drag coefficient and have a profound effect on the near wake.

Forced Patterns of Sea Level Rise in the Community Earth System Model Large Ensemble From 1920 to 2100

AbstractTo provide context for observed sea level rise, the forced response (FR) in dynamic sea level (DSL) during the 20th and 21st centuries is examined in the Community Earth System Model Large Ensemble (LE). After accounting for simulation drift, which in the LE is sizable, the DSL FR is found to be complex, both in space and time. Its evolving character is suggested to arise from both the diversity and transient evolution of climate forcing agents and the slow adjustment timescales of the intermediate and deep oceans. Nonetheless, various intervals of spatially coherent change simulated for the recent past and near future are identified, and their characteristics and associated driving mechanisms are identified and discussed. The mid‐ to late‐20th century DSL FR is characterized by an hemispherically asymmetric pattern of change, with depressed rates of rise in the northern oceans. There is also a dipole of change in the Southern Ocean caused by changes in near‐surface zonal winds. Through the late 20th and early 21st centuries, a different pattern of rise emerges with elevated rates in the tropics and depressed rates at high latitudes. Zonal and interbasin variations characterize both intervals and involve the pattern and depth of anomalous ocean heat content storage and spatial contrasts in the expansion coefficient tied mainly to base state temperature, with greater rates of rise in warm regions per unit warming. The relative roles of surface flux and ocean convergence anomalies are examined.

Ketamine anaesthesia induces gain enhancement via recurrent excitation in granular input layers of the auditory cortex.

Ketamine is a common anaesthetic agent used in research and more recently as medication in treatment of depression. It has known effects on inhibition of interneurons and cortical stimulus-locked responses, but the underlying functional network mechanisms are still elusive. Analysing population activity across all layers within the auditory cortex, we found that doses of this anaesthetic induce a stronger activation and stimulus-locked response to pure-tone stimuli. This cortical response is driven by gain enhancement of thalamocortical input processing selectively within granular layers due to an increased recurrent excitation. Time-frequency analysis indicates a higher broadband magnitude response and prolonged phase coherence in granular layers, possibly pointing to disinhibition of this recurrent excitation. These results further the understanding of ketamine's functional mechanisms, which will improve the ability to interpret physiological studies moving from anaesthetized to awake paradigms and may lead to the development of better ketamine-based depression treatments with lower side effects. Ketamine is commonly used as an anaesthetic agent and has more recently gained attention as an antidepressant. It has been linked to increased stimulus-locked excitability, inhibition of interneurons and modulation of intrinsic neuronal oscillations. However, the functional network mechanisms are still elusive. A better understanding of these anaesthetic network effects may improve upon previous interpretations of seminal studies conducted under anaesthesia and have widespread relevance for neuroscience with awake and anaesthetized subjects as well as in medicine. Here, we investigated the effects of anaesthetic doses of ketamine (15mgkg-1 h-1 i.p.) on the network activity after pure-tone stimulation within the auditory cortex of male Mongolian gerbils (Meriones unguiculatus). We used laminar current source density (CSD) analysis and subsequent layer-specific continuous wavelet analysis to investigate spatiotemporal response dynamics on cortical columnar processing in awake and ketamine-anaesthetized animals. We found thalamocortical input processing within granular layers III/IV to be significantly increased under ketamine. This layer-dependent gain enhancement under ketamine was not due to changes in cross-trial phase coherence but was rather attributed to a broadband increase in magnitude reflecting an increase in recurrent excitation. A time-frequency analysis was indicative of a prolonged period of stimulus-induced excitation possibly due to a reduced coupling of excitation and inhibition in granular input circuits - in line with the common hypothesis of cortical disinhibition via suppression of GABAergic interneurons.

Improving SAR-Based Coherent Change Detection Products by Using an Alternate Coherency Formalism

Low coherence due to signal imbalance between the paired images introduces false alarm for the conventional coherent change detection (CCD) products when the actual change is not present. This letter presents a technique to evaluate and compensate for such degrading CCD effects by enhancing clutter coherence where required. Accordingly, a new correlation formula is also presented for general SAR covariance/coherency data computations.

Small Scale Landslide Detection Using Sentinel-1 Interferometric SAR Coherence

Infrastructure is operational under normal circumstances and is designed to cope with common natural disruptions such as rainfall and snow. Natural hazards can lead to severe problems at the areas where such phenomena occur, but also at neighboring regions as they can make parts of a road network virtually impassable. Landslides are one of the most devastating natural hazards worldwide, triggered by various factors that can be monitored via ground-based and/or satellite-based techniques. Cyprus is in an area of high susceptibility to such phenomena. Currently, extensive field campaigns including geotechnical drilling investigations and geophysical excavations are conducted to monitor land movements, and, at the same time, determine the geological suitability of areas. Active satellite remote sensors, namely Synthetic Aperture Radar (SAR), have been widely used for detecting and monitoring landslides and other ground deformation phenomena using Earth Observation based techniques. This paper aims to demonstrate how the use of Copernicus open-access and freely distributed datasets along with the exploitation of the open-source processing software SNAP (Sentinel’s Application Platform), provided by the European Space Agency, can be used for landslide detection, as in the case study near Pissouri, where a landslide was triggered by heavy rainfall on 15 February 2019, which caused a major disturbance to everyday commuters since the motorway connecting the cities of Limassol and Paphos remained closed for more than a month. The Coherent Change Detection (CCD) methodology was applied successfully by detecting the phenomenon under study accurately, using two indicators (the coherence difference and the normalized coherence difference). Receiver Operating Characteristic (ROC) analysis was carried out to measure their performance with the coherence difference having an overall accuracy of 93% and the normalized coherence difference having an overall accuracy of 94.8% for detecting the landslide and non-landslide areas. The probability of landslide detection was 63.2% in the case of the coherence difference and increased to 73.7% for the normalized coherence difference, whereas the probability of false alarm for both indicators was approximately 1%.

Detection of Crop Seeding and Harvest through Analysis of Time-Series Sentinel-1 Interferometric SAR Data

Synthetic aperture radar (SAR) is more sensitive to the dielectric properties and structure of the targets and less affected by weather conditions than optical sensors, making it more capable of detecting changes induced by management practices in agricultural fields. In this study, the capability of C-band SAR data for detecting crop seeding and harvest events was explored. The study was conducted for the 2019 growing season in Temiskaming Shores, an agricultural area in Northern Ontario, Canada. Time-series SAR data acquired by Sentinel-1 constellation with the interferometric wide (IW) mode with dual polarizations in VV (vertical transmit and vertical receive) and VH (vertical transmit and horizontal receive) were obtained. interferometric SAR (InSAR) processing was conducted to derive coherence between each pair of SAR images acquired consecutively in time throughout the year. Crop seeding and harvest dates were determined by analyzing the time-series InSAR coherence and SAR backscattering. Variation of SAR backscattering coefficients, particularly the VH polarization, revealed seasonal crop growth patterns. The change in InSAR coherence can be linked to change of surface structure induced by seeding or harvest operations. Using a set of physically based rules, a simple algorithm was developed to determine crop seeding and harvest dates, with an accuracy of 85% (n = 67) for seeding-date identification and 56% (n = 77) for harvest-date identification. The extra challenge in harvest detection could be attributed to the impacts of weather conditions, such as rain and its effects on soil moisture and crop dielectric properties during the harvest season. Other factors such as post-harvest residue removal and field ploughing could also complicate the identification of harvest event. Overall, given its mechanism to acquire images with InSAR capability at 12-day revisiting cycle with a single satellite for most part of the Earth, the Sentinel-1 constellation provides a great data source for detecting crop field management activities through coherent or incoherent change detection techniques. It is anticipated that this method could perform even better at a shorter six-day revisiting cycle with both satellites for Sentinel-1. With the successful launch (2019) of the Canadian RADARSAT Constellation Mission (RCM) with its tri-satellite system and four polarizations, we are likely to see improved system reliability and monitoring efficiency.

Testing experimental designs in liquid chromatography (I): Development and validation of a method for the comprehensive inspection of experimental designs

The basis of interpretive optimisation in liquid chromatography is the prediction of resolution, from appropriate solute retention models. The reliability of the process depends critically on the quality of the experimental design. This work develops, validates and applies a general methodology aimed to evaluate the quality of any training experimental design, which will be applied in Part II to design optimisation. The methodology is based on the systematic evaluation of the uncertainties associated to the prediction of retention times in comprehensive scans of both isocratic and gradient experimental conditions. It is able to evaluate comprehensively experimental designs of arbitrary complexity. Five common training experimental designs were used to model the retention, according to the Linear Solvent Strength (LSS) and the Neue-Kuss (NK) equations, using a set of 14 sulphonamides of different polarity. The results are presented in terms of relative uncertainties in predictions, which provide significant and interpretable results. The magnitude of such uncertainties, together with the systematic, coherent and logical changes observed at increasing solute hydrophobicity, give support to the results. The NK model gave smaller errors and unbiased predictions, whereas the LSS model gave rise to lack of fit. Isocratic training designs, which are widely accepted as the most informative, are confirmed as the best. As a general conclusion, gradients are predicted with intrinsically smaller uncertainties, independently of the training experimental design. In addition, gradients are more insensitive than isocratic predictions with regard to the type of training design used. Isocratic predictions deteriorate quickly with mobile phase composition. This explains the better performance of gradient predictions, even with biased models.

Connections between the Long-Period Variability Modes of Both Temperature and Depth of the Upper Mixed Layer of the North Atlantic and the Climate Variability Indices

The interannual–multidecadal variability of the temperature and depth of the upper mixed layer (UML) in the North Atlantic (NA) is analyzed on the basis of the ORA-S3 ocean reanalysis data for 1959–2011. A large part of the UML in the NA is characterized by warming and thinning in all seasons in the period under study. After removing a linear trend, the UML temperature and depth anomalies in individual seasons are decomposed into empirical orthogonal functions (EOF). It is found that the three leading EOFs describe more than 50% of the total variability of the UML temperature and depth. The structure of the first EOF is horseshoe-shaped; this EOF represents coherent changes in the UML temperature and depth throughout the NA, which manifest themselves the year round. This mode corresponds to the Atlantic multidecadal oscillation. The spatial structure of the second EOF in the winter–spring period is a tripole and is caused by the North Atlantic Oscillation (NAO). The time coefficient of the second EOF of the UML temperature in the NA and the NAO index strongly correlate both synchronously and when the NAO index is 11 years ahead. The second EOF of the UML temperature in the summer–autumn period is associated with the Atlantic meridional mode. The third EOF is typical for the UML temperature fluctuations in January and corresponds to the East Atlantic Pattern.

Mapping rainstorm erosion associated with an individual storm from InSAR coherence loss validated by field evidence for the Atacama Desert

AbstractExtreme high‐magnitude and low‐frequency storm events in arid zones provide the necessary runoff to entrain sediments from source areas and therefore dictate the linkages between hillslopes and channels. Nevertheless, the erosive impact of large storms remains difficult to predict. Most of the uncertainty lies in the lack of topographic change maps associated with single hydro‐meteorological events. Consequently, event‐based erosion models are poorly constrained and their extrapolation over long time periods remains uncertain. In this study, a 15‐month Sentinel‐1A coherence time series, optical and field data are used to map the spatial patterns of erosion after the 5‐day storm occurred on March 2015, in the Atacama Desert. The coherence change detection (CCD) analysis suggests that temporal loss of coherence is related to variations in soil moisture, while permanent loss of coherence is related to modification of soil texture by erosion and sedimentation. Importantly, permanent loss of coherence is more apparent on gentle rather than steeper slopes, likely reflecting differences in regolith cover and thickness. These findings can contradict the landscape models predicting higher erosion on steeper hillslopes. The CCD technique represents a promising tool for analysing and modelling sediment connectivity in arid areas, giving a clear picture of the relation between sediment sources and sink pathways. © 2020 John Wiley &amp; Sons, Ltd.

Reduce coherence loss in coherence-assisted transformation

We discuss the coherence-assisted transformation of pure coherent states under incoherent operations and show that the amount of coherence loss can be reduced with the help of the auxiliary coherent state. Starting with the simplest case i.e., the main coherent state and auxiliary coherent state are both 2×2 dimensional, we compare the change of coherence before and after the transformation and find that the amount of coherence loss can be reduced due to the increase of the coherence of auxiliary coherent state. In general, when the main coherent state and auxiliary coherent state are high-dimensional, the result is also true. For the coherence of auxiliary coherent state is increased, we can get the maximally coherent state at some conditions, this case can be viewed as a new way for the distillation of coherent state. These interesting results of coherence transformation will give us a better understanding of the resource manipulation.

Lifespan associated global patterns of coherent neural communication

Healthy ageing is accompanied by changes to spontaneous electromagnetic oscillations. At the macroscopic scale, previous studies have quantified the basic features, e.g., power and frequencies in rhythms of interest from the perspective of attention, perception, learning and memory. On the other hand, signatures and modes of neural communication have recently been argued to be identifiable from global measures applied on neuro-electromagnetic data such as global coherence that quantifies the degree of togetherness of distributed neural oscillations and metastability that parametrizes the transient dynamics of the network switching between successive stable states. Here, we demonstrate that global coherence and metastability can be informative measures to track healthy ageing dynamics over lifespan and together with the traditional spectral measures provides an attractive explanation of neuronal information processing. Finding normative patterns of brain rhythms in resting state MEG would naturally pave the way for tracking task relevant metrics that could crucially determine cognitive flexibility and performance. While previously reported observations of a reduction in peak alpha frequency and increased beta power in older adults are reflective of changes at individual sensors (during rest and task), global coherence and metastability pinpoint the underlying coordination dynamics over multiple brain areas across the entire lifespan. In addition to replication of the previous observations in a substantially larger lifespan cohort than what was previously reported, we also demonstrate, for the first time to the best of our knowledge, age related changes in coherence and metastability in signals over time scales of neuronal processing. Furthermore, we observed a marked frequency dependence in changes in global coordination dynamics, which, coupled with the long-held view of specific frequency bands subserving different aspects of cognition, hints at differential functional processing roles for slower and faster brain dynamics.

Acute mitragynine administration suppresses cortical oscillatory power and systems theta coherence in rats.

Mitragynine is the major alkaloid of Mitragyna speciosa (kratom) with potential as a therapeutic in pain management and in depression. There has been debate over the potential side effects of the drug including addiction risk and cognitive decline. To evaluate the effects of mitragynine on neurophysiological systems function in the prefrontal cortex (PFC), cingulate cortex (Cg), orbitofrontal cortex, nucleus accumbens (NAc), hippocampus (HIP), thalamus (THAL), basolateral amygdala (BLA) and ventral tegmental area of rats. Local field potential recordings were taken from animals at baseline and for 45 min following mitragynine administration (10 mg/kg, intraperitoneally). Drug-induced changes in spectral power and coherence between regions at specific frequencies were evaluated. Mitragynine-induced changes in c-fos expression were also analyzed. Mitragynine increased delta power and reduced theta power in all three cortical regions that were accompanied by increased c-fos expression. A transient suppression of gamma power in PFC and Cg was also evident. There were no effects of mitragynine on spectral power in any of the other regions. Mitragynine induced a widespread reduction in theta coherence (7-9 Hz) that involved disruptions in cortical and NAc connectivity with the BLA, HIP and THAL. These findings show that mitragynine induces frequency-specific changes in cortical neural oscillatory activity that could potentially impact cognitive functioning. However, the absence of drug effects within regions of the mesolimbic pathway may suggest either a lack of addiction potential, or an underlying mechanism of addiction that is distinct from other opioid analgesic agents.

Use of optical and radar remote sensing satellites for identifying and monitoring active/inactive landforms in the driest desert in Saudi Arabia

Observing Earth from the space is key for monitoring land-surface dynamics and probing near-surface geomorphic and geological features, including those obscured by sand sheets/dunes and human activity. The hyper-arid area of the Arabian Peninsula was selected for detecting and extracting obscure paleohydrological systems and modeling the spatio-temporal dynamics of sand dunes using synthetic aperture radar (SAR) and optical high-resolution remote sensing images. Interferometric synthetic aperture radar (InSAR) coherence change detection (CCD) using Sentinel-1 imagery was performed, revealing subtle changes in the surficial landforms of the study area. These images also discriminated between active and inactive geomorphic features. In addition, low-frequency L-band Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar (ALOS/PALSAR) and Shuttle Radar Topography Mission (SRTM) data revealed the details of paleochannels in the basins that drain into the Arabian Gulf. These ephemeral rivers are the source of sand that was later reshaped into dunes by aeolian processes. The results also revealed that the morphology and extension of dunes were clearly influenced by topography, slope, and wind velocity and direction, rather than human activities. Knowledge gained by exploring desert features is essential for planning settlements and development, and integrated approaches using a variety of remote sensing datasets are key for enhancing Earth observation across a range of spatial and temporal scales.

Influence of the Statistical Properties of Phase and Intensity on Closure Phase

Nonzero closure phase exists in multilooked pixels. We study the influence of the statistical properties of the intensity and phase changes of single-looked pixels on multilooked phase and coherence. By quantifying the extent of their influences on phase triplet, we show in this article that the statistical properties of the intensity of pixels within a multilooking window can induce changes in interferometric phase and coherence, and contribute to the nonzero closure phase. We demonstrate that the intensity-induced changes increase by increasing the standard deviation of the phase changes, dispersion index of intensity, and the correlation between the intensity and phase changes. We have used ALOS Phased Array type L-band Synthetic Aperture Radar (PALSAR), ALOS-2 PALSAR-2, and Sentinel-1 images to generate real and semisynthetic interferograms to assess our findings. The semisynthetic interferograms are produced by pairing real SAR data and synthetic SAR data; the synthetic SAR data are generated from the real data by adding random vectors with predefined average changes of phase and intensity. Our results show that closure phase is only a function of the statistical properties of the phase and intensity of pixels, and does not possess the information about the magnitude of physical changes. This casts doubt on the effectiveness of methods that exploit phase triplet as a means to estimate soil moisture or any other deforming or nondeforming changes.