Spatiotemporal Properties Research Articles

IP3 R2 null mice display a normal acquisition of somatic and neurological development milestones.

Astrocytes are key players in the regulation of brain development and function. They sense and respond to the surrounding activity by elevating their intracellular calcium (Ca2+ ) levels. These astrocytic Ca2+ elevations emerge from different sources and display complex spatio-temporal properties. Ca2+ elevations are spatially distributed in global (soma and main processes) and/or focal regions (microdomains). The inositol 1,4,5-trisphosphate receptor type 2 knockout (IP3 R2 KO) mouse model lacks global Ca2+ elevations in astrocytes, and it has been used by different laboratories. However, the constitutive deletion of IP3 R2 during development may trigger compensating phenotypes, which could bias the results of experiments using developing or adult mice. To address this issue, we performed a detailed neurodevelopmental evaluation of male and female IP3 R2 KO mice, during the first 21days of life, as well as an evaluation of motor function, strength and neurological reflexes in adult mice. Our results show that male and female IP3 R2 KO mice display a normal acquisition of developmental milestones, as compared with wild-type (WT) mice. We also show that IP3 R2 KO mice display normal motor coordination, strength and neurological reflexes in adulthood. To exclude a potential compensatory overexpression of other IP3 Rs, we quantified the relative mRNA levels of all 3 subtypes, in brain tissue. We found that, along with the complete deletion of Itpr2, there is no compensatory expression of Itpr1 or Itrp3. Overall, our results show that the IP3 R2KO mouse is a reliable model to study the functional impact of global IP3 R2-dependent astrocytic Ca2+ elevations.

Quantum metasurfaces with atom arrays

Metasurfaces mold the flow of classical light waves by engineering sub-wavelength patterns from dielectric or metallic thin films. We describe and analyze a method in which quantum operator-valued reflectivity can be used to control both spatio-temporal and quantum properties of transmitted and reflected light. Such a quantum metasurface is realized by preparing and manipulating entangled superposition states of atomically thin reflectors. Specifically, we show that such a system allows for massively parallel quantum operations between atoms and photons and for the generation of highly non-classical states of light, including photonic GHZ and cluster states suitable for quantum information processing. We analyze the influence of imperfections and decoherence, as well as specific implementations based on atom arrays excited into Rydberg states. Finally, the extension to quantum metamaterials and emulations of quantum gravitational background for light are discussed.

Negative afterimages facilitate the detection of real images

Negative, or complementary afterimages are experienced following brief adaptation to chromatic or achromatic stimuli, and are believed to be formed in the post-receptoral layers of the retinae. Afterimages can be cancelled by the addition of real images, suggesting that afterimages and real images are processed by similar mechanisms. However given their retinal origin, afterimage signals represented at the cortical level might have different spatio-temporal properties from their real images counterparts. To test this we determined whether afterimages reduce the contrast threshold of added real images, i.e. produce the classic “dipper” function characteristic of contrast discrimination, a behavior believed to be cortically mediated. Stimuli were chromatic and achromatic disks on a grey background. Observers adapted for 1.0 s to two side-by-side disks of a particular color. Following stimulus offset, a test disk added to one side was ramped downwards for 1.5 s to approximately match the temporal characteristic of the afterimage, and the observer was required to indicate the side containing the test disk. The test hue/brightness was either the same as that of the afterimage or a different hue/brightness. The independent variable was the contrast of the adaptor. A dipper followed by masking was observed in most conditions in which the afterimage and test colors had the same hue or brightness. We conclude that afterimages are represented similarly to their real image counterparts at the cortical level.

Local and Long-Range Transport Dust Storms Over the City of Ahvaz: A Survey Based on Spatiotemporal and Geometrical Properties

Particulate matter (PM) represents a criteria air pollutant (CAP) influencing health, climate, cloud properties, economy, agriculture, and the environment. Numerous studies on this subject have classified dust events based on wind speed, visibility, and PM10 levels. The purpose of this study was to evaluate PM10 with a wider range of meteorological parameters and CAPs during different dust storms. Moreover, spatiotemporal and geometrical properties of dust storms were analyzed over the city of Ahvaz between 2012 and 2015. Meteorological parameters included those obtained from the Iran Meteorological Organization (IMO) as well as CAPs from the Ahvaz Environmental Protection Organization (AEPO). During the study period, 68 dust storms were investigated, with sources identified by the AEPO. The highest levels of PM10 were 2877.2, 1327, 2146, 2094, and 1218 µg m−3 during local storms (LS), dusts from Iraq (DI), dust from both sources (DBS), and 1 and 2-peak dust events, respectively. The criteria levels of wind speed, relative humidity, and air temperature also shifted 3 h forward when the severity of dust storms decreased and their durations increased. Strong correlation coefficients (R2) were observed between PM2.5 and PM10 ranging from 0.88 to 0.95 for dust storms falling within each of the five classifications. The highest ascending and the lowest descending slopes belonged to dusts from DBS (600.3 µg m−3 h−1) and DI (73 µg m−3 h−1), respectively. These results have relevance to planning and mitigation strategies for combating different types of dust storms in Ahvaz.

Full 3D + 1 modeling of tilted-pulse-front setups for single-cycle terahertz generation

The tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase-matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. A 3 D + 1 ( x , y , z , t ) numerical model is necessary in order to fully investigate the terahertz generation problem in the tilted-pulse-front scheme. We compare in detail the differences among 1 D + 1 , 2 D + 1 , and 3 D + 1 models. The simulations show that the size of the optical beam in the pulse-front-tilt plane sensitively affects the spatiotemporal properties of the terahertz electric field. The terahertz electric field is found to have a strong spatial dependence such that a few-cycle pulse is generated only near the apex of the prism. Even though the part of the beam farther from the apex can contain a large fraction of the energy, the terahertz waveform shows less few-cycle character. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments such as terahertz acceleration, coherent control of antiferromagnetic spin waves, and terahertz high-harmonic generation.

Routing of strongly confined terahertz spoof surface plasmon polaritons on metasurfaces along straight and curved pathways with subwavelength width.

In search of new technologies for optimizing the performance and space requirements of electronic and optical micro-circuits, the concept of spoof surface plasmon polaritons (SSPPs) has come to the fore of research in recent years. Due to the ability of SSPPs to confine and guide the energy of electromagnetic waves in a subwavelength space below the diffraction limit, SSPPs deliver all the tools to implement integrated circuits with a high integration rate. However, in order to guide SSPPs in the terahertz frequency range, it is necessary to carefully design metasurfaces that allow one to manipulate the spatio-temporal and spectral properties of the SSPPs at will. Here, we propose a specifically designed cut-wire metasurface that sustains strongly confined SSPP modes at terahertz frequencies. As we show by numerical simulations and also prove in experimental measurements, the proposed metasurface can tightly guide SSPPs on straight and curved pathways while maintaining their subwavelength field confinement perpendicular to the surface. Furthermore, we investigate the dependence of the spatio-temporal and spectral properties of the SSPP modes on the width of the metasurface lanes that can be composed of one, two or three cut-wires in the transverse direction. Our investigations deliver new insights into downsizing effects of guiding structures for SSPPs.

Sensory inflow manipulation induces learning-like phenomena in motor behavior.

Perceptual and goal-directed behaviors may be improved by repetitive sensory stimulations without practice-based training. Focal muscle vibration (f-MV) modulating the spatiotemporal properties of proprioceptive inflow is well-suited to investigate the effectiveness of sensory stimulation in influencing motor outcomes. Thus, in this study, we verified whether optimized f-MV stimulation patterns might affect motor control of upper limb movements. To answer this question, we vibrated the slightly tonically contracted anterior deltoid (AD), posterior deltoid (PD), and pectoralis major muscles in different combinations in forty healthy subjects at a frequency of 100Hz for 10min in single or repetitive administrations. We evaluated the vibration effect immediately after f-MV application on upper limb targeted movements tasks, and one week later. We assessed target accuracy, movement mean and peak speed, and normalized Jerk using a 3D optoelectronic motion capture system. Besides, we evaluated AD and PD activity during the tasks using wireless electromyography. We found that f-MV may induce increases (p < 0.05) in movement accuracy, mean speed and smoothness, and changes (p < 0.05) in the electromyographic activity. The main effects of f-MV occurred overtime after repetitive vibration of the AD and PD muscles. Thus, in healthy subjects, optimized f-MV stimulation patterns might over time affect the motor control of the upper limb movement. This finding implies that f-MV may improve the individual's ability to produce expected motor outcomes and suggests that it may be used to boost motor skills and learning during training and to support functional recovery in rehabilitation.

Compartmentalized β1-adrenergic signalling synchronizes excitation-contraction coupling without modulating individual Ca2+ sparks in healthy and hypertrophied cardiomyocytes.

β-adrenergic receptors (βARs) play pivotal roles in regulating cardiac excitation-contraction (E-C) coupling. Global signalling of β1ARs up-regulates both the influx of Ca2+ through sarcolemmal L-type Ca2+ channels (LCCs) and the release of Ca2+ from the sarcoplasmic reticulum (SR) through the ryanodine receptors (RyRs). However, we recently found that β2AR stimulation meditates 'offside compartmentalization', confining β1AR signalling into subsarcolemmal nanodomains without reaching SR proteins. In the present study, we aim to investigate the new question, whether and how compartmentalized β1AR signalling regulates cardiac E-C coupling. By combining confocal Ca2+ imaging and patch-clamp techniques, we investigated the effects of compartmentalized βAR signalling on E-C coupling at both cellular and molecular levels. We found that simultaneous activation of β2 and β1ARs, in contrast to global signalling of β1ARs, modulated neither the amplitude and spatiotemporal properties of Ca2+ sparks nor the kinetics of the RyR response to LCC Ca2+ sparklets. Nevertheless, by up-regulating LCC current, compartmentalized β1AR signalling synchronized RyR Ca2+ release and increased the functional reserve (stability margin) of E-C coupling. In circumstances of briefer excitation durations or lower RyR responsivity, compartmentalized βAR signalling, by increasing the intensity of Ca2+ triggers, helped stabilize the performance of E-C coupling and enhanced the Ca2+ transient amplitude in failing heart cells. Given that compartmentalized βAR signalling can be induced by stress-associated levels of catecholamines, our results revealed an important, yet unappreciated, heart regulation mechanism that is autoadaptive to varied stress conditions.

Spatiotemporal dynamics of multi-vesicular release is determined by heterogeneity of release sites within central synapses

A synaptic active zone (AZ) can release multiple vesicles in response to an action potential. This multi-vesicular release (MVR) occurs at most synapses, but its spatiotemporal properties are unknown. Nanoscale-resolution detection of individual release events in hippocampal synapses revealed unprecedented heterogeneity among vesicle release sites within a single AZ, with a gradient of release probability decreasing from AZ center to periphery. Parallel to this organization, MVR events preferentially overlap with uni-vesicular release (UVR) events at sites closer to an AZ center. Pairs of fusion events comprising MVR are also not perfectly synchronized, and the earlier event tends to occur closer to AZ center. The spatial features of release sites and MVR events are similarly tightened by buffering intracellular calcium. These observations revealed a marked heterogeneity of release site properties within individual AZs, which determines the spatiotemporal features of MVR events and is controlled, in part, by non-uniform calcium elevation across the AZ.

Multi-Resolution Simulations of HIV Glycan Shield Reveal Mechanistic Aspects of Immune Evasion

Dense arrangement of N-glycans on the HIV-1 envelope (Env) protein masks the underlying antigenic surfaces and acts as a shield from the adaptive immune system. In addition, extreme heterogeneity of these glycans makes the Env glycoprotein recalcitrant to structural studies relevant for vaccine design efforts. Here, we have performed extensive atomistic and coarse-grained (CG) molecular dynamics simulations to elucidate the spatio-temporal properties of the glycan shield in conjunction with the associated glycosylation diversity of the Env. We have optimally parameterized different Env glycoforms using a CG model adapted from the MARTINI-2.2 forcefield. This newly developed model, not only captured most of the atomistic findings, but allowed the exploration of the glycosylation patterns over long time scales. This is the first time to our knowledge such a multi-resolution model was built having native glycosylation pattern including both oligomannose and complex glycans. These simulations were combined with an in-house graph-theory based approach to quantify the glycan shielding behavior over microsecond time scales. We find that the glycan network connectivity remains stable when all the glycans are decorated with just oligomannose as often considered in most of the published studies to-date. However, with native glycosylation (decorated with both complex mannose glycans), we find immunologically more relevant results. Some of the glycans reorganize their orientations over time to enhance the shielding over antigenic regions, eventually leading to evasion from antibodies. In addition, in the presence of glycans, large-scale dimension reduction analyses indicate a blooming and twisting motion of the underlying protein as the backbone slightly rearranges towards a more stable glycosylated trimeric Env conformation.

Spatiotemporal Properties of Sub‐Rayleigh and Supershear Ruptures Inferred From Full‐Field Dynamic Imaging of Laboratory Experiments

AbstractMany earthquakes propagate at sub‐Rayleigh speeds. Earthquakes propagating at supershear speeds, though less common, are by far more destructive. Hence, it is important to quantify the motion characteristics associated with both types of earthquake ruptures. Here we report on the spatiotemporal properties of dynamic ruptures measured in our laboratory experiments using the dynamic digital image correlation technique. Earthquakes are mimicked by the frictional rupture propagating along the interface of two Homalite plates. Digital images of the propagating ruptures are captured by an ultrahigh‐speed camera and processed with digital image correlation in order to produce sequences of evolving displacement and velocity maps. Our measurements reveal the full‐field structure of the velocity components, bridge the gap between previous spatially sparse velocimeter measurements available only at two to three locations, and enable us to quantify the attenuation patterns away from the interface.

Spatiotemporal properties of whisker-evoked tactile responses in the mouse secondary somatosensory cortex

The representation of rodents’ mystacial vibrissae within the primary somatosensory (S1) cortex has become a major model for studying the cortical processing of tactile sensory information. However, upon vibrissal stimulation, tactile information first reaches S1 but also, almost simultaneously, the secondary somatosensory cortex (S2). To further understand the role of S2 in the processing of whisker inputs, it is essential to characterize the spatio-temporal properties of whisker-evoked response dynamics in this area. Here we describe the topography of the whiskers representation in the mouse S2 with voltage sensitive dye imaging. Analysis of the spatial properties of the early S2 responses induced by stimulating individually 22 to 24 whiskers revealed that they are spatially ordered in a mirror symmetric map with respect to S1 responses. Evoked signals in S2 and S1 are of similar amplitude and closely correlated at the single trial level. They confirm a short delay (~3 ms) between S1 and S2 early activation. In both S1 and S2 caudo-dorsal whiskers induce stronger responses than rostro-ventral ones. Finally, analysis of early C2-evoked responses indicates a faster activation of neighboring whisker representations in S2 relative to S1, probably due to the reduced size of the whisker map in S2.

High order mode structure of intense light fields generated via a laser-driven relativistic plasma aperture

The spatio-temporal and polarisation properties of intense light is important in wide-ranging topics at the forefront of extreme light-matter interactions, including ultrafast laser-driven particle acceleration, attosecond pulse generation, plasma photonics, high-field physics and laboratory astrophysics. Here, we experimentally demonstrate modifications to the polarisation and temporal properties of intense light measured at the rear of an ultrathin target foil irradiated by a relativistically intense laser pulse. The changes are shown to result from a superposition of coherent radiation, generated by a directly accelerated bipolar electron distribution, and the light transmitted due to the onset of relativistic self-induced transparency. Simulations show that the generated light has a high-order transverse electromagnetic mode structure in both the first and second laser harmonics that can evolve on intra-pulse time-scales. The mode structure and polarisation state vary with the interaction parameters, opening up the possibility of developing this approach to achieve dynamic control of structured light fields at ultrahigh intensities.

EchoBERT: A Transformer-Based Approach for Behavior Detection in Echograms

Monitoring fish welfare has become increasingly important for salmon farmers. Current approaches require manual labor and physical inspection or interpretation of video. Echo sounders make real-time monitoring of the entire fish population over time possible. However, current approaches for automatic interpretation of echograms mainly focus on species classification and therefore fail to appropriately encode the spatiotemporal properties contained within the data. Other approaches are primarily aimed at the feeding process and require a human-in-the-loop. Transformer-based approaches have been shown to better handle long sequences than Long Short-Term Memory networks in recent Natural Language Processing research. We therefore introduce EchoBERT - Echo Bidirectional Encoder Representation Transformer, a transformer-based approach for behavior detection in farmed Atlantic salmon ( Salmo salar, Salmonidae ), using the spatiotemporal properties contained in echograms. The model interprets the spatiotemporal dynamics of echograms through attention mechanisms to classify fish behavior. We compare EchoBERT to a traditional sequence modeling approach on the task of detecting behavior indicative of pancreas disease in a six-fold cross-validation study using data from 6 distinct farming cages. We show that EchoBERT shows a strong correlation between model predictions and true labels, indicated by a Matthew’s Correlation Coefficient score of 0.694 ± 0.178 using an ensemble approach, compared to 0.626 ± 0.084 for traditional sequence models. We also find that EchoBERT is capable of detecting disease indicators over a month prior to detection using standard procedures. Our results show that EchoBERT has high potential for automatic behavior detection through unintrusive methods suitable for applications in aquaculture. The source code is available at: https://gitlab.com/hakonma/echobert .

Compression of laser pulses by near-forward Raman amplification in plasma

We propose a new scheme for compression of ultrashort laser pulses enabled by Near-Forward Raman Amplification (NFRA) in plasma. In contrast to traditional forward Raman amplification in plasma, the seed pulse in NFRA propagates faster than the pump through manipulation of the spatiotemporal properties of the pump beam. A “π-pulse” solution similar to that of stimulated Raman backscattering amplification is obtained, indicating that NFRA can be used for compression of ultrashort laser pulses. NFRA is numerically demonstrated with a 2D simulation using a front-tilt near-forward pump pulse.

Toward Universal Neural Interfaces for Daily Use: Decoding the Neural Drive to Muscles Generalises Highly Accurate Finger Task Identification Across Humans

Peripheral neural signals can be used to estimate movement-specific muscle activation patterns for the purpose of human-machine interfacing (HMI). The available HMI solutions, however, provide limited movement decoding accuracy that often results in inadequate device control, especially in the dynamic tasks context, and require extensive algorithm training that is highly subject-specific. Here, we show that dexterous movements can be identified with high accuracy using a physiology-derived and information-theoretically optimised feature space that targets the spatio-temporal properties of the spiking activity of spinal motor neurons (neural features), decomposed from the interference myoelectric signal. Moreover, we show that the movement decoding accuracy based on these neural features is not influenced by the muscle activation level, reaching overall >98% in the full range of forces investigated and from processing intervals as short as 30-ms. Finally, we show that the high accuracy in individual finger movement recognition can be achieved without user-specific models. These results are the first to show a highly accurate discrimination of dexterous movement tasks in a wide range of muscle activation levels from near-real time processing intervals, with minimal subject-specific training, and thus are promising for the translation of HMI to daily use.

Wintertime precipitation in eastern China and relation to the Madden-Julian oscillation: Spatiotemporal properties, impacts and causes

This study investigated the characteristics of wintertime precipitation in eastern China and associated atmospheric circulation based on different Madden-Julian oscillation (MJO) activities. Besides, the underlying causes and impacts of MJO activities on wintertime precipitation in eastern China were explored as well by analyzing large scale atmospheric circulations conditions. The results indicated that: (1) in different MJO phases, distinct differences can be observed in spatial patterns of wintertime precipitation in eastern China, especially in southeastern China. (2) Significant enhanced precipitation can be detected over southeastern China during active MJO events, while precipitation reduced significantly over these regions during inactive MJO events. Enhancement of precipitation during active MJO events was mainly attributed to the increased precipitation on phases 2–4; (3) the impacts of MJO phases on precipitation can be explained by the northeastward propagation of atmospheric pressure pattern over eastern China during active MJO events. This study may provide theoretical knowledge for water resources management and early warning of floods and droughts in eastern China. The potential teleconnections of near-equatorial MJO activities to the subtropics or extratropics precipitation over eastern China were also discussed in this study.

Становление трансцендентизма и трансцендентализма в античной философии

The paper is devoted to the analysis of the formation of transcendentism and transcendentalism in the philosophy of antiquity. It is noted that this kind of research makes it possible to better understand the genesis and foundations of the main variants of metaphysics in classical and post-non-classical thought. It is emphasized that this theoretical model is characterized by the interpretation of the transcendent as a “different” dimension of being, a certain higher sphere located outside our world, which has special spatio-temporal properties and which is incomprehensible to empirical knowledge of people. In turn, the model of the transcendental in ancient philosophy did not provide for the existence of an independent “human cosmos” separate from the outside world. The main purpose of the transcendental method of Socrates, Plato, Aristotle, Stoics, Neoplatonists and other thinkers is to determine the conditions by which it is possible to think from empirical observations. The author concludes that the philosophical standpoint of Plato and Aristotle can be characterized in general as transcendentism with elements of transcendentalism.

An extensible software platform for interdisciplinary cardiovascular imaging research

Background and objectiveCardiovascular imaging is an exponentially growing field with aspects ranging from image acquisition and analysis to disease characterization, and evaluation of therapy approaches.The transfer of innovative new technological and algorithmic solutions into clinical practice is still slow. In addition to the verification of solutions, their integration in the clinical processing workflow must be enabled for the assessment of clinical impact and risks. The goal of our software platform for cardiac image processing – CAIPI – is to support researchers from different specialties such as imaging physics, computer science, and medicine by a common extensible platform to address typical challenges and hurdles in interdisciplinary cardiovascular imaging research. It provides an integrated solution for method comparison, integrated analysis, and validation in the clinical context. The interface concept enables a combination with existing frameworks that address specific aspects of the pipeline, such as modeling (e.g., OpenCMISS, CARP) or image reconstruction (Gadgetron). MethodsIn our platform, we developed a concept for import, integration, and management of cardiac image data. The integration approach considers the spatiotemporal properties of the beating heart through a specific data model. The solution is based on MeVisLab and provides functionalities for data retrieval and storage. Two types of plugins can be added. While ToolPlugins usually provide processing algorithms such as image correction and segmentation, AnalysisPlugins enable interactive data exploration and reporting. GUI integration concepts are presented for both plugin types. We developed domain-specific reporting and visualization tools (e.g., AHA segment model) to enable validation studies by clinical experts. The platform offers plugins for calculating and reporting quantitative parameters such as cardiac function, which can be used to, e.g., evaluate the effect of processing algorithms on clinical parameters. Export functionalities include quantitative measurements to Excel, image data to PACS, and STL models to modeling and simulation tools. ResultsTo demonstrate the applicability of this concept both for method development and clinical application, we present use cases representing different problems along the innovation chain in cardiac MR imaging.Validation of an image reconstruction method (MRI T1 mapping)Validation of an image correction method for real-time 2D-PC MRIComparison of quantification methods for blood flow analysisTraining and integration of machine learning solutions with expert annotationsClinical studies with new imaging techniques (flow measurements in the carotid arteries and peripheral veins as well as cerebral spinal fluid). ConclusionThe presented platform can be used in interdisciplinary teams, in which engineers or data scientists perform the method validation, followed by clinical research studies in patient collectives. The demonstrated use cases show how it enables the transfer of innovations through validation in the cardiovascular application context.

Development and application of the multi-dimensional integrated geography curricula from the perspective of regional remote sensing

ABSTRACT Geography can improve citizens’ quality of life by improving their understanding of the population, resources, environment and development of geographical areas. The emergence of remote sensing technology provides a convenient method for understanding the regional geographical landscape. It is important to develop a regional geography curriculum for college students that includes modern remote sensing technology to cultivate their geographic literacy and popularize remote sensing technology. To focus on the development of college students’ valuable ability to think critically in spatial terms, this paper introduces methods for observing the spatiotemporal properties (multi-temporal, multi-scale, multi-angle), physical properties (multi-spectral, multi-product), and natural synthetic properties (multi-element, multi-media) of regional geography via multi-dimensional means. Taking the construction of a regional remote sensing geography course as an example, this paper discusses the goals, content structure and teaching management construction. Then, the study discusses plans and anticipations for the development of the course. Geographical observations and the teaching of geography from the multi-dimensional perspective will provide innovative methods and better results in terms of college students’ quality of education in higher education curricula.