Extreme Region Research Articles

Calibration of CFOSAT Off‐Nadir SWIM SWH Product Based on CNN‐LSTM Model

AbstractHigh‐precision observation of significant wave height (SWH) is crucial for marine research. The Surface Waves Investigation and Monitoring (SWIM) aboard the China France Oceanography Satellite (CFOSAT) provides the ocean wave spectrum that allows for the calculation of the off‐nadir SWH parameters, but there exists a certain bias with the in‐situ SWH values. To improve the accuracy of the SWH calculation bias from the off‐nadir 6°, 8°, 10° wave spectra and the whole combined spectrum, this paper establishes a spatio‐temporal hybrid model that combines convolutional neural network (CNN) and long short‐term memory network (LSTM). Additionally, to further correct bias exhibited under high sea state, we introduce a bias correction module based on deep neural network (DNN) to adjust the SWIM off‐nadir SWH greater than 4 m. The experimental results demonstrate a significant enhancement in the accuracy of corrected SWIM off‐nadir SWH, and the best calibration result is 10° with 0.267 m root mean square error (RMSE), and 0.979 correlation coefficient (R) compared with the ERA5 value. We conducted a comprehensive study and analysis on the performance of the proposed model under different wave heights, extreme sea states, and wind and swell regions. Meanwhile, the buoy and altimeters are leveraged to render further evaluation the RMSE of the corrected SWH is less than 0.5 m.

Optimizing water and nitrogen management for saline wasteland improvement: A case study on Suaeda salsa

Cultivating Suaeda salsa (S. salsa) is a promising strategy for the improvement and development of saline wastelands. However, the absence of a scientifically reasonable water and fertilizer management system has long hindered the large-scale improvement and utilization of saline wastelands. Therefore, we performed field experiments for two consecutive years to investigate the effects of water-nitrogen coupling on biomass, forage quality, salt absorption capacity, soil improvement effect, and economic benefits of S. salsa. The optimal water and nitrogen dosages for multi-objective optimization were determined using multiple regression and spatial analysis methods. Three irrigation levels were established for the experiment based on 0.35 (W1), 0.50 (W2), and 0.65 (W3) of the local ETo (Where ETo denotes the reference evapotranspiration calculated based on the FAO-56 recommended by the Food and Agriculture Organization). The three nitrogen application levels were 150 (F1), 250 (F2), and 350 (F3) kg ha−1 in the complete combination design. At the same nitrogen application level, the biomass and economic benefits of the W3 irrigation level were the highest. However, the forage quality, salt absorption capacity, salt reduction, and water productivity at the W3 irrigation level were lower than those at the W2 irrigation level, and the water productivity at the W1 irrigation level was the highest. At the same irrigation level, when the nitrogen application level was F2, the biomass, forage quality, salt absorption, salt reduction, and net profit, all reached their maximum values, and water productivity was the highest at the F3 level. The optimal amount of water and nitrogen applied for each parameter was different, so it was impossible to obtain the highest biomass, forage quality, salt absorption, salt reduction, water productivity, and net profit at the same time. Therefore, multi-objective optimization was needed, the optimal irrigation volume range was 3350.11–3485.97 m3 ha−1, and the nitrogen application rate range was 273.49–326.66 kg ha−1. These findings provide a scientific basis for the large-scale cultivation of S. salsa in extreme arid region, which is helpful for the improvement and utilization of saline-alkali land.

Combining Morphological Characteristics and DNA Barcoding Techniques Confirm Sea Urchins of the Genus Echinometra (Echinodermata: Echinoidea) in Marine Habitat Located at Extreme Regions of the Caribbean Sea.

Echinometra spp. are pantropical echinoids found in benthic marine habitat throughout the Caribbean, Atlantic, and Indo-West Pacific oceanic regions. Currently, morphology and molecular data are sparse for echinoids observed along the northeastern coast of Toco, Trinidad, where they are relatively common. Additionally, accurate species identity for Echinometra spp. remains dynamic at both northernmost and southernmost parts of the Caribbean Sea. Although distribution of sea urchins in the genus Echinometra have extensively been studied throughout the Atlantic and Indo-West Pacific, information on its range of distribution at the edge of the Caribbean Sea is lacking. In this study, the mitochondrial Cytochrome c Oxidase subunit I (mt COI) gene was amplified using polymerase chain reaction, then sequenced. Based on successfully obtained gene sequences for 581 base pairs, the echinoid species Echinometra lucunter and Echinometra viridis were identified for black and red color morphotypes from Trinidad (n=23) and Key Largo, Florida (n=6), respectively. Furthermore, these specimens were genetically identical to species identified in other studies for Puerto Rico, Panamá, Honduras, and Belize. Although morphological variations, such as spine and test color occur throughout Echinometra spp., molecular identification using the barcoding technique confirmed E. lucunter color morphs for the first time in Trinidad. Since the status of E. lucunter populations, specifically at the most northern and southern regions of the Caribbean Sea is dynamic, further studies using gene markers are essential in determining species distribution, in light of current trends in climate change.

Segmentation-free measurement of locomotor frequency in Caenorhabditis elegans using image invariants.

An animal's locomotor rate is an important indicator of its motility. In studies of the nematode C. elegans, assays of the frequency of body bending waves have often been used to discern the effects of mutations, drugs, or aging. Traditional manual methods for measuring locomotor frequency are low in throughput and subject to human error. Most current automated methods depend on image segmentation, which requires high image quality and is prone to errors. Here, we describe an algorithm for automated estimation of C. elegans locomotor frequency using image invariants, i.e., shape-based parameters that are independent of object translation, rotation, and scaling. For each video frame, the method calculates a combination of 8 Hu's moment invariants and a set of Maximally Stable Extremal Regions (MSER) invariants. The algorithm then calculates the locomotor frequency by computing the autocorrelation of the time sequence of the invariant ensemble. Results of our method show excellent agreement with manual or segmentation-based results over a wide range of frequencies. We show that compared to a segmentation-based method that analyzes a worm's shape and a method based on video covariance, our technique is more robust to low image quality and background noise. We demonstrate the system's capabilities by testing the effects of serotonin and serotonin pathway mutations on C. elegans locomotor frequency.

Rise in water vapour driven by moisture transport facilitates water availability for the greening of global deserts

There are substantial changes in the global drylands owing to climate change and anthropogenic activities. However, this aspect is not adequately explored in the context of recent climate change and global warming. Therefore, we analyse the role of water vapour in driving precipitation and corresponding surface greenness in the global deserts using satellite measurements. Statistical techniques such as partial correlation and Randon Forest (RF) are employed to understand the relationship among the physical processes that drive water availability for desert greening. Our analysis shows that water vapour is relatively lower (<25 kg/m2) in the deserts than rest of the globe, but comparable to the polar and high-altitude regions. Among the deserts, Thar (25 kg/m2) and Sahara (15–20 kg/m2) show higher water vapour, in contrast to the American and Gobi deserts (<10 kg/m2). Trajectory analysis reveals that water vapour transport from the south Atlantic Ocean is very high (90 kg/m/s) to the Sahel region of Sahara. Similarly, water vapour comes from Arabian Sea and Indian Ocean to Thar, mainly during Indian Summer Monsoon (ISM). There is an increase in water vapour driven by a rise in moisture transport to the American, Arabian, Thar and Sub-Sahara deserts during the period 2003–2020. The rise in moisture transport and associated water vapour in the deserts enhance water availability through precipitation and soil moisture, influencing surface greenness, as illustrated by the partial correlation and RF analyses. Enhanced water vapour and water availability, together with anthropogenic activities such as agriculture and afforestation in the deserts drive greening, which is more pronounced in Thar and Sub-Sahara. This study, thus, reveals the role of atmospheric moisture in regulating the terrestrial water availability and surface greenness in the extreme arid regions on the earth.

Gastrointestinal nematodes in Cuniculus paca (Linnaeus, 1766) from hunting fauna in the Western Amazonian region

Cuniculus paca, commonly known as the paca, is a rodent of the Cuniculidae family that is widely distributed throughout the Americas, including all Brazilian territories, and is abundant in the Amazon region. It is one of the most hunted species and faces significant predation in the extreme western Amazon region of Brazil because it constitutes a staple in the diet of local communities, for subsistence and commercial purposes. Understanding the helminthic fauna of these animals is of paramount importance, given that some nematodes have zoonotic potential and may pose risks to consumer health. This study aimed to contribute to the records of the nemtodes of this highly consumed species in the Amazon region, highlighting the occurrence of gastrointestinal parasites in free-living pacas intended for human subsistence consumption. The study was conducted in the Paranã da Floresta community, located in the municipality of Guajará, Amazonas from 2022 to 2023. The community members hunted this rodent for consumption and voluntarily provided the viscera for analysis. Nematodes were extracted from each organ. The organs were opened, and the contents were processed using a sieve (0.15 mm) and subsequently evaluated separately. In total, 10,157 nematodes were found in the 14 pacas. Based on morphological analyses, the nematodes were identified as Heligmostrongylus sedecimradiatus (n = 10,068), Trichuris sp. (n = 85), and Physaloptera sp. (n = 4). This study provides insights into the nematodes diversity of free-living pacas in the extreme Western Amazon region, emphasizing the importance of sanitary surveillance and public awareness of the risks associated with bushmeat consumption.

Superficial femoral artery pseudoaneurysm at implantation site of drug eluting stent discovered due to bacteremia: A case report

BACKGROUND Drug-eluting stents (DES) are used to treat lower extremity arterial disease. During DES treatment, aneurysmal degeneration occasionally occurs, especially with fluoropolymer-based DES. However, the incidence of pseudoaneurysms after DES placement is rarely reported in the lower extremity region, although there have been several reports on pseudoaneurysm formation after DES pla-cement in the coronary artery region. CASE SUMMARY We report the case of a 64-year-old man who presented with fever and pain in his left hand after dialysis. Bacteremia was diagnosed by blood culture, and after admission, he developed pain on the medial side of the right thigh. A pseudoaneurysm was observed in the right superficial femoral artery (SFA) at the proximal end of a previously placed DES. The bacteremia was thought to have been caused by a pseudoaneurysm of the left superficial brachial artery, and the pseudoaneurysm of the left superficial brachial artery was removed after antibiotic treatment. The pseudoaneurysm of the right SFA rapidly expanded after admission, but the expansion rate was reduced after infection control. Seven months after the first admission, the pseudoaneurysm of the left SFA was re-moved and in situ revascularization performed using a rifampicin-soaked Dacron graft. CONCLUSION Although pseudoaneurysm after DES placement in the lower extremity region is rare, it must be considered in patients with bacteremia.

Comprehensive assessment of five near-real-time satellite precipitation products in the Lower Yangtze River Basin and the Lixiahe region, China: Dual perspectives from time series and extreme events

Near real-time satellite precipitation products (NSPPs) have significant potential in meteorological hydrological monitoring and forecasting due to their timeliness. Previous evaluation-oriented studies have either focused on the uncertainty of time series or on the monitoring capability of extreme events. There is limited research that comprehensively considers both aspects to provide a systematic knowledge. Moreover, there is still insufficient understanding of the accuracy of hourly precipitation estimates. This study conducts a comprehensive evaluation between five NSPPs (IMERG Early, IMERG Late, GSMaP NRT, GSMaP NRT Gauge and PERSIANN CCS) from two main perspectives at hourly scale: an assessment of time series spanning from 2018 to 2022 over the Lower Yangtze River Basin and the Lixiahe region and an examination of the four extreme events over the Tai Lake Basin and the Chao Lake Basin. HP-metrics are proposed to evaluate bias in the location of extreme rainfall, rainy area, and precipitation amount over time, comprehensively analyzing performance in terms of extreme events. The results show that, for general and seasonal assessment, IMERG Late generally performed best with good statistical metrics, with the highest CSI (0.343), CC (0.445), KGE ‘(0.295) in annual results, and the best agreement in capturing convective rain diurnal curves (summer CC = 0.820). GSMaP showed a better detection capability especially in spring and summer, and also performed better in capturing frequency curves, but always showed large estimation errors. IMERG and GSMaP detected worse CC region close to the water body. And the effect of high terrain on GSMaP NRT is more obvious in winter. For the evaluation in detecting the extreme events, IMERG and GSMaP overestimated the area and intensity and had a certain ability to discriminate the location of extreme precipitation, based on the temporal variation of HP-metrics. The rapid expansion or contraction of the extent of the extreme precipitation region could degrade the detection capability of HP-π. The comprehensive understanding of NSPPs provides valuable insights for upgrading satellite retrieval algorithms and making informed selection for precipitation products in meteorological hydrological applications.

Injury Risk Predictions in Lunar Terrain Vehicle (LTV) Extravehicular Activities (EVAs): A Pilot Study

Extravehicular activities will play a crucial role in lunar exploration on upcoming Artemis missions and may involve astronauts operating a lunar terrain vehicle (LTV) in a standing posture. This study assessed kinematic response and injury risks using an active muscle human body model (HBM) restrained in an upright posture on the LTV by simulating dynamic acceleration pulses related to lunar surface irregularities. Linear accelerations and rotational displacements of 5 lunar obstacles (3 craters; 2 rocks) over 5 slope inclinations were applied across 25 simulations. All body injury metrics were below NASA’s injury tolerance limits, but compressive forces were highest in the lumbar (250–550N lumbar, tolerance: 5300N) and lower extremity (190–700N tibia, tolerance: 1350N) regions. There was a strong association between the magnitudes of body injury metrics and LTV resultant linear acceleration (ρ = 0.70–0.81). There was substantial upper body motion, with maximum forward excursion reaching 375 mm for the head and 260 mm for the chest. Our findings suggest driving a lunar rover in an upright posture for these scenarios is a low severity impact presenting low body injury risks. Injury metrics increased along the load path, from the lower body (highest metrics) to the upper body (lowest metrics). While upper body injury metrics were low, increased body motion could potentially pose a risk of injury from flail and occupant interaction with the surrounding vehicle, suit, and restraint hardware.

IMPROVEMENT OF CAPILLAROSCOPY METHOD FOR STUDYING HUMAN MICROCIRCULATION

The human circulatory system has historically captivated researchers in the field of medicine. Modern medicine, however, has moved beyond identifying a single crucial element, such as the heart or venous system, for maintaining blood flow. Instead, it emphasizes a more analytical approach, focusing on the interconnected functioning of all components within the system. The aim of this work is to analyze the existing methods of studying blood microcirculation and to improve the technology of capillaroscopy, technical means of raster microphotography to determine the physiological state and disorders of capillary circulation. To achieve this objective, we address the following tasks: analyzing existing non-invasive methods for studying the human vascular system; enhancing the optical capillaroscopy method through the utilization of modern high-resolution digital cameras, computer, and multimedia equipment, along with appropriate software for analyzing electronic images; developing a technological scheme and equipment design for digital microphotography of capillaries in the periungual region of the upper extremities; providing software solutions for registering and analyzing digital microphotographic images obtained through capillaroscopy; conducting experimental studies to explore the structure and properties of capillaries utilizing the developed technologies and equipment. Magnetic resonance imaging (MRI) enables the comprehensive evaluation of both anatomical and functional aspects of blood flow. Magnetic resonance angiography (MRA) capitalizes on the distinction between the signal emitted by moving tissue (blood) and that of surrounding stationary tissue, facilitating the acquisition of vascular images without the need for radiopaque contrast agents. Ultrasonography integrates Doppler and conventional ultrasound techniques, providing physicians with insights into blood vessel structure and blood flow dynamics. Traditional ultrasound employs sound waves that are imperceptible to the human ear and bounce off blood vessels, while Doppler ultrasound measures the velocity of sound wave reflection from moving elements. Ophthalmoscopy constitutes a fundamental component of standard ophthalmological examinations, serving as a pivotal tool for diagnosing eye conditions and evaluating the condition of blood vessels. Additionally, ophthalmoscopy aids in diagnosing autoimmune disorders. Capillaroscopy enables comprehensive assessments of both systemic and regional microcirculation disorders, facilitating the characterization of tissue metabolism. Dysfunction in capillary function contributes to circulatory impairments, leading to blood stasis, metabolic irregularities, and compromised immunity, thereby exacerbating existing conditions and predisposing individuals to new diseases. Optical computerized capillaroscopy offers a non-invasive means of visualizing, examining, and archiving capillary images, enabling clinicians to make informed assessments regarding blood microcirculation. Experimental validation of the optimized hardware and software capillaroscopy system was conducted using nail bed capillaries of a patient with type II diabetes mellitus undergoing insulin therapy for 10 years. This study underscores the importance of refining and enhancing optical capillaroscopy methodologies by leveraging high-resolution camera sensors and modern computational tools for image processing.

Carbon emission reduction in public buildings of extreme cold regions: A study on enclosure structure and HVAC system parameter optimization

AbstractThe implementation of strategies aimed at curtailing energy consumption and carbon emissions in buildings is of paramount importance. Priority should be accorded to the reduction of embodied carbon emissions from construction materials and operational carbon emissions during the usage phase. A public building situated in an extremely cold region is chosen as the subject of this study. An initial investigation is conducted into the impact of various enclosure structure materials on embodied carbon. The impact of different heating, ventilation and air conditioning (HVAC) systems on the total carbon emissions of public buildings are studied as well. The findings indicate that the amalgamation of W3 + R + G4 + H4 culminates in the least total carbon emissions. Upon establishing the foundational scheme for the public building, an optimization (nondominated sorting genetic algorithm II [NSGA II] and Criteria Importance Through Intercrieria Correlation [CRITIC]) of the enclosure structure parameters is initiated to examine the optimal parameters of the public building's enclosure structure. The findings reveal that a decrease in the heat transfer coefficient could trigger an increase in total carbon emissions. This is attributed to the fact that the carbon emissions embodied in the production process of these materials could potentially outweigh the reduction observed in operational carbon emissions. Further adjustments were also made to the parameters of the HVAC system in the buildings. The findings indicate that within the context of public buildings, given the presence of optimal parameters and an HVAC system that utilizes solar energy for both heating and cooling in the American Society of Heating, Refrigerating and Air‐Conditioning Engineers, Inc. 6 A climatic zone, the efficiency of the cooling system can exert a significant influence on the operations carbon emissions reduction.

Continuum emission from within the plunging region of black hole discs

ABSTRACT The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however, find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component, but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin which must be low a• &amp;lt; 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our continuum fitting model is made publicly available.

Spatial shaping of low- and high-order harmonics generated using vortex beams

We demonstrate the generation of the low- and high-order harmonic vortex beams from a single spiral phase plate illuminated by different laser wavelengths. The second harmonic (532 nm) originates from the application of the wavefront-structured 1064 nm femtosecond pulses with fractional orbital angular momentum (OAM) during propagation through a lithium triborate crystal, while the third harmonic (500 nm) originates from the application of the wavefront-structured near-IR (1500 nm) femtosecond pulses with integer OAM during propagation through a 150 μm thick fused silica plate. The topological charges (TCs) of the second and third harmonics are measured and compared. The increase in TC and the peculiarities in OAM variations during modification of the polarisation of the incident radiation are analysed and discussed. The two-colour-pump-driven second-harmonic vortex radiation interacted with an Ar gas jet to generate vortex harmonics up to the 14th order with double-lobe complex spatial profiles in the extreme ultraviolet region.

Estimating water balance in a Brazilian semiarid watershed using different spatial data

This study advances water balance (WB) estimation in the Paraguaçu River watershed, Brazil, by leveraging spatial data to mitigate the challenges of sparse monitoring, particularly in the semiarid region. By combining precipitation (PPT) and actual evapotranspiration (ETR) data from diverse methodologies, including IMERG, TMPA, TerraClimate (TC), and IDW interpolation, alongside ETR sources like MOD16, GLEAM, and TerraClimate, we aim to capture the watershed's physical and climatic nuances. The analysis reveals that TerraClimate data (PPTTC and ETRTC) most accurately reflect spatial variations, effectively capturing orographic effects and the semiarid climate, thus emerging as the optimal combination for depicting WB (WBTC_TC). Key findings highlight the variable precision of PPT and ETR data sources in characterizing spatial distribution and magnitude across the watershed, with TerraClimate data showing superior sensitivity to regional disparities. This sensitivity is crucial for accurately modeling the hydrological dynamics in regions with contrasting climatic conditions, from humid orographic areas to the semiarid zones. Moreover, the study underscores the importance of data validation and careful integration of spatial data, particularly in under-monitored or climatically extreme regions, to enhance the reliability of hydrological analyses. The successful integration of spatial data underscores its value in remote or data-scarce regions, reinforcing the necessity for rigorous spatial and temporal validation. This approach not only improves water management strategies but also enriches the integration with climatic and hydrological models, offering a comprehensive toolkit for addressing the complexities of watershed management in the face of climate variability.

Distribution dynamics and quantile dynamic convergence of the digital economy: Prefecture-level evidence in China

The digital-substantive fusion is the realistic need to crack the problem of “out of the real to the virtual” in the real economy. Based on the panel data of 288 prefecture-level cities in China from 2011 to 2019, we use kernel density estimation and quantile convergence model to explore the distribution dynamics and convergence trend of the digital economy across the country and in the eastern, central, and western regions. In doing so, we unearth several key findings. First, the development of the digital economy in Chinese cities is on the rise, but absolute differences among cities still exist. Second, the overall development of the digital economy exhibits a dynamic q-σ convergence trend, but the development of the digital economy in the central region from the 0.75 to 0.95 quantiles shows a divergence trend. Third, our analysis reveals quantile heterogeneity and regional heterogeneity in the dynamic absolute q-β convergence of digital economy development. The tendency to converge is stronger in the extreme quantile regions than in other regions, while the convergence speed of central and western regions is higher than that of eastern regions. Finally, the dynamic conditional q-β convergence trend of digital economy development across the country and in the eastern, central, and western regions is stronger than the dynamic absolute q-β convergence, with the trend of convergence weakening only in the eastern high quantile regions. These findings provide empirical evidence for promoting regional coordinated high-quality development of digital economy, as well as theoretical references for vigorously promoting the construction of a modernized industrial system and accelerating the development of new-quality productive forces.

A microdosimetry analysis of reversible electroporation in scattered, overlapping, and cancerous cervical cells

We present a numerical method for studying reversible electroporation on normal and cancerous cervical cells. This microdosimetry analysis builds on a unique approach for extracting contours of free and overlapping cervical cells in the cluster from the Extended Depth of Field (EDF) images. The algorithm used for extracting the contours is a joint optimization of multiple-level set function along with the Gaussian mixture model and Maximally Stable Extremal Regions. These contours are then exported to a multi-physics domain solver, where a variable frequency pulsed electric field is applied. The trans-Membrane voltage (TMV) developed across the cell membrane is computed using the Maxwell equation coupled with a statistical approach, employing the asymptotic Smoluchowski equation. The numerical model was validated by successful replication of existing experimental configurations that employed low-frequency uni-polar pulses on the overlapping cells to obtain reversible electroporation, wherein, several overlapping clumps of cervical cells were targeted. For high-frequency calculation, a combination of normal and cancerous cells is introduced to the computational domain. The cells are assumed to be dispersive and the Debye dispersion equation is used for further calculations. We also present the resulting strength-duration relationship for achieving the threshold value of electroporation between the normal and cancerous cervical cells due to their size and conductivity differences. The dye uptake modulation during the high-frequency electric field electroporation is further advocated by a mathematical model.

On extreme quantile region estimation under heavy-tailed elliptical distributions

Consider the estimation of an extreme quantile region corresponding to a very small probability. Estimation of extreme quantile regions is important but difficult since extreme regions contain only a few or no observations. In this article, we propose an affine equivariant extreme quantile region estimator for heavy-tailed elliptical distributions. The estimator is constructed by extending a well-known univariate extreme quantile estimator. Consistency of the estimator is proved under estimated location and scatter. The practicality of the developed estimator is illustrated with simulations and a real data example.

Detecting Wear and Tear in Pedestrian Crossings Using Computer Vision Techniques: Approaches, Challenges, and Opportunities

Pedestrian crossings are an essential part of the urban landscape, providing safe passage for pedestrians to cross busy streets. While some are regulated by timed signals and are marked with signs and lights, others are simply marked on the road and do not have additional infrastructure. Nevertheless, the markings undergo wear and tear due to traffic, weather, and road maintenance activities. If pedestrian crossing markings are excessively worn, drivers may not be able to see them, which creates road safety issues. This paper presents a study of computer vision techniques that can be used to identify and classify pedestrian crossings. It first introduces the related concepts. Then, it surveys related work and categorizes existing solutions, highlighting their key features, strengths, and limitations. The most promising techniques are identified and described: Convolutional Neural Networks, Histogram of Oriented Gradients, Maximally Stable Extremal Regions, Canny Edge, and thresholding methods. Their performance is evaluated and compared on a custom dataset developed for this work. Insights on open issues and research opportunities in the field are also provided. It is shown that managers responsible for road safety, in the context of a smart city, can benefit from computer vision approaches to automate the process of determining the wear and tear of pedestrian crossings.

Space–Time Characterization of Extreme Precipitation Indices for the Semiarid Region of Brazil

Various indices of climate variability and extremes are extensively employed to characterize potential effects of climate change. Particularly, the semiarid region of Brazil is influenced by adverse effects of these changes, especially in terms of precipitation. In this context, the main objective of the present study was to characterize the regional trends of extreme precipitation indices in the semiarid region of Brazil (SAB), using daily precipitation data from the IMERG V06 product, spanning the period from 1 January 2001 to 31 December 2020. Twelve extreme precipitation indices were considered, which were estimated annually, and their spatial and temporal trends were subsequently analyzed using the nonparametric Mann–Kendall test and Sen’s slope. The analysis revealed that the peripheral areas of the SAB, especially in the northwest and extreme south regions, exhibited higher intensity and frequency of extreme precipitation events compared to the central portion of the area. However, a negative trend in event intensity was noted in the north, while positive trends were identified in the south. The frequency of extreme events showed a predominance of negative trends across most of the region, with an increase in consecutive dry days particularly throughout the western SAB. The average total precipitation index was above 1000 mm in the north of the SAB, whereas in the central region, the precipitation averages were predominantly below 600 mm, with rainfall intensity values ranging between 6 and 10 mm/day. Over the span of 20 years, the region underwent an average of 40 consecutive dry days in certain localities. A negative trend was observed in most of the indices, indicating a reduction in precipitation intensity in future decades, with variations in some indices. The dry years observed towards the end of the analyzed period likely contributed to the observed negative trends in the majority of extreme precipitation indices. Such trends directly impact the intensity and frequency of extreme weather events in the SAB. The study is important for highlighting and considering the impacts of changes in precipitation extremes in the semiarid region of Brazil. Based on the obtained results, we advocate the implementation of public policies to address future challenges, such as incorporating adaptations in water resource management, sustainable agricultural practices, and planning for urban and rural areas.

Recent advances in high-order harmonic generation from laser-ablated plumes at the advanced laser light source laboratory

High-order harmonic generation is a nonlinear optical frequency conversion process that occurs during intense ultrafast laser-matter interaction. At the Advanced Laser Light Source laboratory, we use ultrafast laser pulses having diverse wavelengths, spanning visible, near- and mid-infrared ranges, to generate high-order harmonics from laser-ablated plumes in the extreme ultraviolet or soft X-ray region of the electromagnetic spectrum. The Advanced Laser Light Source Laboratory is situated within the Énergie Matériaux Télécommunications Center of the Institut national de la recherche scientifique in Montréal, Quebec, Canada. We focus on generating bright and broadband harmonics by exploiting various types of ultrafast resonances in different species within the laser-ablated plume, and use them for applications in ultrafast spectroscopy, imaging, and AMO science. We are also actively exploring previously unknown physics governing the harmonic generation from different resonances. In this review article, we provide an overview of the recent advancements made in these directions.