Search Results (64)

Soil erosion poses a significant global environmental challenge, causing land degradation, deforestation, river siltation, and reduced agricultural productivity. Although the Revised Universal Soil Loss Equation (RUSLE) has been widely applied in Brazil, its use in the tropical river basins of the Amazon remains limited. This study aimed to apply a GIS-integrated RUSLE model and compare its soil loss estimates with multiple linear regression (MLR) models based on terrain attributes, aiming to identify priority areas and key geomorphometric drivers of soil erosion in a tropical Amazonian river basin. A digital elevation model based on Shuttle Radar Topography Mission (SRTM) data, land use and land cover (LULC) maps, and rainfall and soil data were applied to the GIS-integrated RUSLE model; we then defined six risk classes—slight (0–2.5 t ha⁻¹ yr⁻¹), slight–moderate (2.5–5), moderate (5–10), moderate–high (10–15), high (15–25), and very high (>25)—and identified priority zones as those in the top two risk classes. The Caeté River Basin (CRB) was classified into six erosion risk categories: low (81.14%), low to moderate (2.97%), moderate (11.88%), moderate to high (0.93%), high (0.03%), and very high (3.05%). The CRB predominantly exhibited a low erosion risk, with higher erosion rates linked to intense rainfall, gentle slopes covered by Arenosols, and human activities. The average annual soil loss was estimated at 2.0 t ha⁻¹ yr⁻¹, with a total loss of 1005.44 t ha⁻¹ yr⁻¹. Additionally, geomorphological and multiple linear regression (MLR) analyses identified seven key variables influencing soil erosion: the convergence index, closed depressions, the topographic wetness index, the channel network distance, and the local curvature, upslope curvature, and local downslope curvature. These variables collectively explained 26% of the variability in soil loss (R² = 0.26), highlighting the significant role of terrain characteristics in erosion processes. These findings indicate that soil erosion control efforts should focus primarily on areas with Arenosols and regions experiencing increased anthropogenic activity, where the erosion risks are higher. The identification of priority erosion areas enables the development of targeted conservation strategies, particularly for Arenosols and regions under anthropogenic pressure, where the soil losses exceed the tolerance threshold of 10.48 t ha⁻¹ yr⁻¹. These findings directly support the formulation of local environmental policies aimed at mitigating soil degradation by stabilizing vulnerable soils, regulating high-impact land uses, and promoting sustainable practices in critical zones. The GIS-RUSLE framework is supported by consistent rainfall data, as verified by a double mass curve analysis (R² ranging from 0.64 to 0.77), and offers a replicable methodology for soil conservation planning in tropical basins with similar erosion drivers. This approach offers a science-based foundation to guide soil conservation planning in tropical basins. While effective in identifying erosion-prone areas, it should be complemented in future studies by dynamic models and temporal analyses to better capture the complex erosion processes and land use change impacts in the Amazon. Full article

Background/Objectives: Although the COVID-19 pandemic has largely concluded, the varied trajectories it has followed in different regions of the world remain incompletely understood. Intensive research is needed to fully grasp its course and the implications for future global health challenges. Notably, the milder trajectory of the COVID-19 pandemic in Sub-Saharan Africa has defied initial predictions. An emerging body of evidence suggests that, in addition to the continent’s younger average age and the lower prevalence of relevant comorbidities, co-infections with helminths may have also impressively shaped the pandemic’s milder trajectory in the region. Indeed, helminths are renowned for their ability to modulate human immune responses, which, while potentially beneficial in limiting excessive inflammation, could also diminish vaccine efficacy and impede viral clearance. This study investigated different aspects of the intricate interactions between COVID-19 and Lymphatic Filariasis (LF), a helminth infection caused by parasitic worms such as Wuchereria bancrofti, Brugia malayi, and Brugia timori and endemic to various regions in Sub-Saharan Africa and the tropics. Methods: For this purpose, samples of a larger and ongoing clinical trial (ethical approval codes: CHRPE/AP/525/17 and 325/21; trial registration number ISRCTN14042737) were collected from 222 individuals from endemic areas of Ghana, along with comprehensive clinical and demographic data. The samples include LF patients (n = 222) grouped according to their Lymphoedema (LE) stages, as well as COVID-19 vaccinated (n = 81) and non-vaccinated individuals (n = 141). All vaccinated participants received the COVID-19 vaccine ChAdOx1-S (also known as Vaxzevria) developed by the University of Oxford and AstraZenca. The expressions of SARS-CoV-2 and filarial-specific antibodies (IgG, IgA) were accessed using ELISA, while Luminex-based immunoassays were employed to measure the expression of SARS-CoV-2 variant-specific neutralizing antibodies. The interplay between vaccine responses and demographic factors was analyzed using group comparisons with the Kruskal-Wallis or Mann-Whitney U tests. Results: The results indicate that a remarkable portion of unvaccinated individuals (56% IgA seropositive, 39% IgG seropositive) developed antibodies against SARS-CoV-2 despite no confirmed infection. Notably, the study identified a robust antibody response to COVID-19 vaccination, which was independent of the degree of LF pathology or parasitic status. An important observation was the reduced SARS-CoV-2 antibody response in individuals seropositive for Ascaris lumbricoides (p = 0.0264), highlighting an interaction between roundworm infection and COVID-19. Conclusions: The study concludes that the ChAdOx1-S COVID-19 vaccine (AstraZeneca) triggers a strong immune response in LF patients; however, filarial and/or soil-transmitted helminth seropositivity might influence the COVID-19 infection-induced response. These findings emphasize the complexity of infectious disease dynamics in co-infected populations and the need to decipher parasite-induced immunomodulatory mechanisms on COVID-19 vaccination. Full article

Implementation of RSV prevention strategies requires an understanding of seasonal virus epidemiology; yet, such data are lacking in many tropical regions. We describe the seasonality and environmental factors associated with RSV activity in Machala, Ecuador. From July 2018 to July 2023, we analyzed nasopharyngeal samples from children younger than 5 years with an acute respiratory illness using Biofire FilmArray v.1.7™. Meteorological data were obtained from Ecuador’s Instituto Nacional de Meteorología e Hidrología. RSV detection was associated with mean outdoor air temperature (threshold 27 °C, area under the curve (AUC) 0.74, p < 0.001) that was even stronger when using a 4-week lag (threshold 27 °C, AUC 0.865, p < 0.001) and with precipitation greater than 0.5 mm/week using a 6-week lag (p = 0.008). This finding could provide guidance for the ideal timing to improve RSV surveillance and implement RSV prevention measures in Machala, including universal administration of extended half-life monoclonal antibody to infants entering their first RSV season. Full article

Neglected Tropical Diseases are a group of 25 conditions caused by diverse agents. They mostly affect people with poorer health outcomes, particularly preventable diseases. The social determinants of health influence the development and progression of these poverty diseases, with inadequate sanitation presenting chronicity, high morbidity, and economic impacts. Chagas disease, a prominent Neglected Tropical Disease caused by the intracellular pathogen Trypanosoma cruzi, is endemic in Latin America but is increasing as a global concern due to population migration. It is transmitted through insect vectors, congenitally, orally via contaminated food and beverage, via transfusions and organ donation, and due to laboratory accidents, among other minor relevant routes. As a silent illness, with many infected individuals remaining asymptomatic, it contributes to underdiagnosis, and delayed treatment that involves nitro derivatives is often discontinued due to side effects. Chagas disease spreads in non-endemic areas like the United States of America and Europe. Blood screening practices vary, with endemic regions implementing universal testing, while non-endemic areas rely on selective methods. Recent innovations, such as riboflavin–ultraviolet light treatment and arylimidamide compounds, represent promising alternatives to reduce transfusion transmission. This review presents an analysis of Trypanosoma cruzi transmission through blood and derivatives, addressing the main routes, globally implemented control strategies, and recent advancements in blood bank safety. Full article

Water erosion has severe impacts on soil and the carbon cycle. In tropical regions, it is significantly influenced by rainfall, soil erodibility, rapid changes in land use and land cover (LULC), and agricultural management practices. Understanding the dynamics of water erosion is essential for implementing precise land degradation control. This study aimed to estimate soil and soil organic carbon (SOC) losses due to water erosion over five years in a coffee-producing area in Brazil using the revised universal soil loss equation (RUSLE). The results revealed that average soil losses in coffee plantation areas ranged from 1.77 to 1.80 Mg ha⁻¹ yr⁻¹, classified as very low. Total and potential soil loss ranged from 2184.60 to 6657.14 Mg ha⁻¹, a 305% difference, demonstrating the efficiency of vegetative cover (C factor) and conservation practices (P factor) in reducing soil loss rates. SOC losses were less than 200 kg ha⁻¹ yr⁻¹, with averages of 17.67 and 13.00 kg ha⁻¹ yr⁻¹ in coffee areas. In conclusion, agricultural management practices, such as the presence of native vegetation, maintaining vegetative cover in coffee rows, contour planting, and improving agronomic techniques, are essential for reducing soil and SOC losses, even in scenarios of biennial alternation in coffee production. Thus, sustainable agricultural management plays a crucial role in mitigating water erosion, maintaining productivity, and addressing climate change. Full article

Papaya (Carica papaya L.) is a highly nutritious fruit crop cultivated commercially in the tropical and subtropical regions of the world. Being a shallow rooted fruit crop, it requires frequent application of nutrients. Papaya is highly remunerative due to its high productivity and responds positively to nutrient application. Papaya Ring Spot Virus (PRSV) is a major threat to papaya production, which causes severe yield loss and reduces fruit quality. To combat PRSV and enhance productivity, a nutrient formulation was developed by combining organic, inorganic nutrient sources with biocontrol agents to improve the health and vigor of the plants. Experiments were conducted to standardize the application time and evaluate the efficacy of nutrient formulation in enhancing yield, and to combat papaya ring spot virus (PRSV) incidence in papaya from January 2021 to December 2023 at Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India. The results revealed that foliar application of nutrient formulation at monthly intervals from the 3rd to the 7th month after planting (MAP) along with regular application of recommended dose of fertilizers (RDF) at bimonthly intervals from the 3rd MAP significantly increased the yield (37.79% and 30.57% in TNAU Papaya CO 8 and Red Lady, respectively) and reduced PRSV disease incidence (22.49% in TNAU Papaya CO 8 and 16.53% in Red Lady). Metabolomics study indicates that foliar spray of nutrient formulation enhanced the activators and precursors of defense enzymes, viz., peroxidase (PO), polyphenol oxidase (PPO), phenyl ammonia lyase (PAL), catalase (CAT) and nitrate reductase (NRase) in the sprayed plants over unsprayed control. Therefore, the sprayed plants exhibited tolerance to PRSV incidence by maintaining vigor and induced systemic resistance by the defense enzymes. Full article

Anesthesiology, the medical specialty that deals with the management of vital functions in patients undergoing surgery, has played an important role in the successful development of cardiac interventions worldwide. Tracing the historical roots of cardiac anesthesia and critical care from its inception in the late 1950s, a paradigm shift in perioperative care has been driven by a better understanding of the mechanisms of organ dysfunction in stressful conditions and technological advances regarding surgical approach, patient monitoring, and organ protection. Although progress in cardiac anesthesia and critical care lagged a little behind in Caribbean territories, successful achievements have been accomplished over the last forty years. Compared with Western countries, the greater prevalence of obesity, diabetes mellitus, and hypertension as well as specific diseases such as cardiac amyloidosis, sickle cell anemia, rheumatic heart disease, and tropical infections may reduce a patient’s physiologic reserve and increase the operative risk among the multi-ethnic population living in the French West Indies and Guiana. So far, cardiac anesthesiologists at the University Hospital of Martinique have demonstrated their abilities in implementing evidence-based clinical care processes and adaptating to efficiently working in a complex environment interacting with multiple partners. Attracting specialized physicians in dedicated cardiac surgical centers and the creation of a regional health network supported by governmental authorities, insurance companies, and charitable organizations are necessary to solve the unmet needs for invasive cardiac treatments in the Caribbean region. Full article

Heart rate variability biofeedback (HRV BF) training aids adaptation to new climatic, geographical, and social environments. Neurophysiological changes during the HRV BF in individuals from tropical regions studying in the Arctic are not well understood. The aim of this study was to research electroencephalographic (EEG) changes during a single short-term HRV BF session in Indian and Russian students studying in the Russian Arctic. The Indian (n = 40) and Russian (n = 40) healthy students (age 19–21 years) at a medical university in Arkhangelsk (64°33′ N 40°32′ E) were studied. HRV and EEG parameters were measured at baseline (5 min) and during a short-term HRV BF session (5 min) to increase the total power (TP, ms²) of the HRV spectrum. The baseline heart rate and stress index levels were significantly higher in the Indian students. During the HRV BF sessions, the sympathetic activity decreased more significantly in Russian students, while the alpha EEG activity significantly increased across all brain regions in both groups. In Indian students, there was a notable increase in theta and beta1 EEG spectral power in the frontal, central, and temporal regions. HRV BF training in Indian students was associated with a more pronounced activation of brain systems compared with Russian students. Full article

Few studies have focused on the infectious complications in kidney transplant recipients in tropical regions, particularly in the Caribbean. The primary objective of this study was to determine the incidence of bacterial, fungal, and parasitic infections in kidney transplant recipients in the French Caribbean and French Guiana. We included all patients who received a kidney transplant at the University Hospital of Guadeloupe between January 2014 and October 2016, with post-transplant follow-up in the French Caribbean. A total of 91 patients were included, of whom 57 developed an infectious event during follow-up. When infections were documented (94/111), bacterial infections were the most frequent (79/94), followed by fungal (11/94) and parasitic infections (4/94). Four cases of nocardiosis were identified (4/79). Phaeohyphomycosis was the most common fungal infection (7/11). In a multivariate analysis, the female gender and diabetes mellitus at the time of transplant were significantly associated with a higher risk of infection. This study is the first to describe the epidemiology of infections in kidney transplant recipients in the Caribbean and to analyze the potential risk factors. We reported a similar profile of bacterial infections to that which were observed in the European and American studies. However, we found a higher incidence of tropical infections, such as nocardiosis and phaeohyphomycosis, which highlights the need for heightened awareness among healthcare teams to ensure earlier and more appropriate treatment. Further studies focusing on these rare tropical infections are necessary to better understand their risk factors Full article

As a significant global source of vegetable oil, the oil palm’s ability to withstand abiotic stresses, particularly drought, is crucial for sustainable agriculture. This is especially significant in tropical regions, where water scarcity is becoming more common. Nitrogen, a vital nutrient, plays an essential role in various physiological and biochemical processes in plants, directly influencing growth and stress tolerance. This study investigates the interaction between nitrogen sources (ammonium vs. nitrate) and drought stress in oil palm (Elaeis guineensis) seedlings, which is critical in enhancing productivity in this economically important crop. The experiment evaluated five commercial oil palm genotypes, which were supplied with nitrogen solutions (15 mM NH₄⁺ or NO₃⁻) for 46 days, followed by 30 days of progressive drought. The results showed that drought conditions universally reduced the biomass, with ammonium-fed plants exhibiting greater shoot biomass sensitivity than nitrate-fed plants. Drought also significantly decreased the chlorophyll a, PhiPS2, and root-reducing sugar levels—critical indicators of photosynthetic efficiency and overall plant health. The effects on the root architecture were complex, with ammonium nutrition differentially influencing the lateral root length under well-watered versus drought conditions, highlighting nitrogen forms’ nuanced role in root development. Importantly, substantial genotypic variability was observed in most traits, affecting the responses to both the nitrogen source and drought stress. This variability suggests that certain genotypes may be better suited to cultivation in specific environmental conditions, particularly drought-prone areas. In conclusion, this study underscores the intricate interplay between nitrogen nutrition, genotypic variability, and drought tolerance in oil palm seedlings. These findings highlight the need to integrate these factors into agricultural management strategies to improve resilience and productivity in oil palm plantations. Full article

Abiotic stressors such as cold temperatures have intensified due to climate change. Cold stress is a crucial factor that restricts the growth of barley in tropical and subtropical regions. Fast chlorophyll a-fluorescence induction (OJIP test) parameters are also used as biological markers for screening cultivars tolerant to abiotic stresses. Therefore, an experiment was conducted over three growing seasons in the research farm of Gonbad Kavous University to identify closely linked quantitative trait loci (QTLs) controlling OJIP test parameters under chilling stress, in the Iranian barley RILs population. For this study, the genome-wide composite interval mapping method was utilized to identify closely linked QTLs associated with OJIP test parameters under chilling stress conditions. Combined analysis of variance showed that the lines had significant differences (p < 0.05) in terms of OJIP test parameters, indicating genetic diversity among the lines. Also, Pearson correlation coefficients showed that grain yield had a significant positive correlation (p < 0.05) with Fm, Fv, ABS/CSm, ETo/CSo, ETo/CSm, REo/CSo, REo/CSm, TRo/CSo and TRo/CSm parameters under chilling stress conditions. Cluster analysis using the WARD method identified 50 lines tolerant to chilling stress. A total of 48 stable and closely linked QTLs related to 12 OJIP test parameters were identified on seven barley chromosomes under chilling stress conditions. Full article

Mangroves grow in intertidal zones in tropical and subtropical regions, offering numerous advantages to humans and ecosystems. Mangrove monitoring is one of the important tasks to understand the current status of mangrove forests regarding their loss issues, including deforestation and degradation. Currently, satellite imagery is widely employed to monitor mangrove ecosystems. Sentinel-2 is an optical satellite imagery whose data are available for free, and which provides satellite imagery at a 5-day temporal resolution. Analyzing satellite images before and after loss can enhance our ability to detect mangrove loss. This paper introduces a LSST-Former model that considers the situation before and after mangrove loss to categorize non-mangrove areas, intact mangroves, and mangrove loss categories using Sentinel-2 images for a limited number of labels. The LSST-Former model was developed by integrating a fully convolutional network (FCN) and a transformer base with few-shot learning algorithms to extract information from spectral-spatial-temporal Sentinel-2 images. The attention mechanism in the transformer algorithm may effectively mitigate the issue of limited labeled samples and enhance the accuracy of learning correlations between samples, resulting in more successful classification. The experimental findings demonstrate that the LSST-Former model achieves an overall accuracy of 99.59% and an Intersection-over-Union (IoU) score of 98.84% for detecting mangrove loss, and the validation of universal applicability achieves an overall accuracy of more than 92% and a kappa accuracy of more than 89%. LSST-Former demonstrates superior performance compared to state-of-the-art deep-learning models such as random forest, Support Vector Machine, U-Net, LinkNet, Vision Transformer, SpectralFormer, MDPrePost-Net, and SST-Former, as evidenced by the experimental results and accuracy metrics. Full article

Thermal comfort is an important subject to evaluate the quality of outdoor environments. This study investigated outdoor thermal conditions and the thermal comfort perception of pedestrians using walkways within a university campus in Thailand, located in the hot and humid tropical region. In this field study, microclimate measurements were conducted to assess the physiological equivalent temperature (PET) of walkways, and on-site questionnaire surveys (n = 400) were used to evaluate the thermal sensation votes of pedestrians in different walkway conditions. The results revealed that the neutral PET was 25.2 °C and its acceptable range was 24.6–32.0 °C. Most pedestrians accept the thermal conditions of all walkway types but at different levels of acceptability, albeit in a slightly warm sensation. Among different walkway types, the cantilever-covered walkway with sparse trees yields the closest PET to the neutral PET. The most comfortable and favorable walkway is that with a lower air temperature, less sunlight, and higher wind ventilation. The studies on the outdoor thermal comfort of pedestrian walkways could benefit urban planners and engineers in designing physical and environmental conditions of walkways as well as promoting non-motorized transport and green university campuses. Full article

In China, the precession of the equinoxes was conceptualized as an “annual difference” (suicha 歲差) between the tropical and sidereal year. The idea was introduced in the fourth century, it saw universal acceptance from the eighth century on, and it was in the four centuries in between that it was tried, debated, and spread whilst a Mediterranean-origin concept thereof arrived from India. Its four-century journey from fringe idea to universal truth is a well-studied point of interest in the history of astronomy. In this article, we will shift focus to the idea’s polymathic protagonists and epistemic foundations to explore how a scientific idea was born, debated, transmitted, and taught in Confucian commentary and, no less important, how politics, geography, regional schools, foreign transmission, and the Buddhist and Daoist religions shaped how thinkers engaged with it as individuals and as communities. Inspired by the work of Chen Kanli and Randall Collins, the goal is to show that there is nothing simple or inexorable about how even an empirically useful tool of predictive astronomical modeling is received in the relevant expert community, as it is but one element in a complex network of people and ideas aligning and opposing in ever-evolving strategies to assert relevance. Full article

Basil (Ocimum species) represents an extraordinary group of aromatic plants that have gained considerable economic importance, primarily due to their essential oils, which have applications in medicine, culinary, and perfumery. The Ocimum genus encompasses more than 60 species of herbs and shrubs originally native to tropical regions. This genus stands out for its remarkable diversity, displaying a wide spectrum of variations in phenotype, chemical composition, and genetic makeup. In addition to genetic factors, the growth, development, and essential oil production of basil are also influenced by environmental conditions, ontogeny, and various other factors. Consequently, the primary objective of this study was to explore the diversity in both the morphological characteristics and essential oil composition among basil genotypes preserved within the gene bank of the Hungarian University of Agriculture and Life Sciences’ Department of Medicinal and Aromatic Plants. The investigation involved the assessment of fifteen basil genotypes, representing four distinct species: Ocimum basilicum (including ‘Anise’, ‘Clove’, ‘Fino Verde’, ‘Licorice’, ‘Mammoth’, ‘Mrs. Burns’, ‘Thai tömzsi’, ‘Thai hosszú’, and ‘Vietnamese basil’), Ocimum sanctum (green holy basils), Ocimum citrodora (Lemon basil), and Ocimum gratissimum (African and Vana holy basil). The genotypes exhibited significant variations in their morphological growth, essential oil content (EOC), and composition. African basil produced more biomass (408.3 g/plant) and showed robust growth. The sweet basil cultivars clove, licorice, Thai tömzsi, and Thai hosszú also exhibited similar robust growth trends. Vietnamese basil, on the other hand, displayed the lowest fresh biomass of 82.0 g per plant. Both holy basils showed EOC levels below 0.5%, while Mrihani basil stood out with the highest EOC of 1.7%. The predominant constituents of the essential oil among these genotypes comprised estragole, thymol, methyl cinnamate, linalool, and eugenol. In conclusion, this study showed that the genotypes of basil stored in the department’s gene bank exhibit a wide range of variability, both within and between species. Full article