Search Results (195)

This study presents a quantitative investigation of substituent effects on the stability of 1:2 complexes formed between para-substituted 2-phenylbenzimidazole ligands and Cu(II) or Co(II) ions. The ligands, featuring hydroxyl (–OH), chloro (–Cl), and nitro (–NO₂) substituents, were synthesized via copper acetate-mediated oxidative cyclization. Stability constants (log K) were determined spectrophotometrically using both the Benesi–Hildebrand and Job methods, which yielded perfectly consistent results and confirmed ML₂ stoichiometry. For both metal series, the stability decreases in the order –OH > –Cl > –NO₂. Excellent linear correlations were obtained between log K and Hammett σ constants, yielding reaction constants of ρ = −0.79 for Cu(II) and ρ = −1.00 for Co(II). These negative ρ values confirm that electron-donating substituents enhance complex stability by increasing electron density on the donor nitrogen. Furthermore, the stability constants for Cu(II) complexes are approximately two orders of magnitude higher than those for Co(II), in agreement with the Irving–Williams series. This work establishes a clear, predictive structure–stability relationship and validates the combined methodological approach for quantifying metal–ligand interactions in tunable benzimidazole systems. Full article

Background: Ectopic pregnancy occurs in about 1–2% of all pregnancies, with 95% implanting in the fallopian tubes. Hepatic implantation is one of the rarest and most dangerous forms of abdominal ectopic pregnancy. Its diagnosis is often delayed because of nonspecific symptoms, and it is also often difficult for routine ultrasound imaging to visualize ectopic pregnancy sites that are not in the pelvis. Since this type of pregnancy carries a risk of severe hemorrhage, early identification is crucial. Case: A 30-year-old woman, gravida 3 para 2, presented with a serum β-hCG of 66,408 mIU/mL, but no intrauterine pregnancy was detected on ultrasound imaging. At an outside facility, a laparoscopy was performed, which also failed to show a pelvic ectopic pregnancy. The patient then received her first dose of methotrexate and was subsequently transferred to a tertiary care center for further evaluation. MRI and liver ultrasound showed a 2.3 cm subcapsular lesion in segment 5 of the liver that was suspicious for a hepatic ectopic pregnancy. However, these imaging studies could not exclude a gestational trophoblastic disease or hepatic neoplasm. A dilation and curettage revealed no trophoblastic tissue. The patient next received two additional doses of methotrexate on hospital days 4 and 7 due to an inadequate decline in interval β-hCG; β-hCG levels declined gradually but steadily over several months until they became undetectable and indicated a successful medical treatment of her hepatic ectopic pregnancy. Conclusions: This case highlights the complex diagnostic and treatment challenges presented by a hepatic ectopic pregnancy. Multimodal imaging, serial monitoring of β-hCG levels, and the engagement of a multidisciplinary team were essential factors in achieving a safe, nonsurgical, and successful resolution of this condition. When a pregnancy of unknown location is suspected, extended imaging studies are critical tools for patient evaluation after initial imaging studies and laparoscopy are inconclusive. Full article

Predictive Digital Soil Mapping (PDSM) in Eastern Amazonia faces challenges due to its environmental complexity, difficult access, and scarce legacy data. While legacy soil maps contain valuable tacit knowledge, updating them requires methods that can handle uncertainty. This study evaluates the integration of old soil maps with machine learning to update soil information in Tracuateua, Pará, with a specific focus on the performance of ensemble learning and the explicit incorporation of uncertainty metrics in soil mapping units under hydromorphic influence, which, in addition to being difficult to access, are influenced by complex pedogenetic processes. We combined 270 sampling points, equivalent to the total pixels that captured the variability of soil mapping units, with environmental covariates and historical data. Several algorithms were tested, including an ensemble approach, to predict mapping units and quantify uncertainty through entropy and confusion indices. The ensemble model demonstrated improved stability and reduced classification uncertainty compared to single models, particularly in challenging hydromorphic environments. Although accuracy gains were modest, the models captured soil–environment relationships, with climate as: Annual Mean Temperature 22,000 years ago (Tmean_22k), relief: Channel Network Base Level (CNBL and altitude) and organism variables: Land Surface Temperature (LST) emerging as the main predictors. Spatialized uncertainty estimates, expressed through entropy and the confusion index, provide a practical decision-support tool for guiding field surveys and identifying areas of low mapping reliability. By explicitly transferring the pedologist’s mental model—encoded as tacit knowledge in legacy soil maps—into ensemble learning, this study presents a robust and transferable framework for updating soil maps in data-scarce tropical regions, balancing predictive performance, spatial consistency, and uncertainty-aware interpretation. Full article

Drought is the primary stress factor in semiarid environments. Consequently, selecting plant genetic resources capable of tolerating temporary periods of water scarcity, such as Physalis angulata, becomes essential. This study aimed to identify P. angulata accessions with potential for use under water deficit conditions by evaluating plant water status and physiological and biochemical responses. Five accessions, including two from Bahia (BA1 and BA2), Pará-PA, Rio de Janeiro-RJ, and Piauí-PI, were grown under well-watered and water deficit conditions. Relative water content, gas exchange parameters, and organic solute accumulation were assessed. All accessions exhibited changes in plant water status and reductions in CO₂ assimilation, stomatal conductance, and leaf transpiration under water deficit. The accumulation of compatible solutes varied among accessions, with notable contrasts between Bahia accession 2 and Pará accession, particularly for total soluble sugars and reducing sugars. These findings highlight the complexity of the species and the distinct mechanisms underlying its response to limited water availability. Overall, gas exchange was the trait most sensitive to water restriction, followed by alterations in biochemical attributes. Therefore, the Physalis angulata accessions from Bahia accession 2 and Pará accession show potential for use under water-deficit conditions and could provide valuable insights, particularly through transcriptome analysis. Full article

Homogeneous Kolbe-Schmitt carboxylation of phenoxides offers a mild and effective alternative to the classical high-temperature solid-phase Kolbe-Schmitt reaction. To develop this into a practical synthetic approach, we investigated several fundamental dependencies, particularly the impact of cations (Na, K, Li, Cs, and Rb), phenoxide concentration, and solvents (DMSO or DMF) on the yield and regioisomeric ratio of hydroxyaromatic carboxylic acids (HACAs). We identified optimal conditions for the effective carboxylation of different phenoxides, including a chiral Ellman’s sulfinamide derived from ortho-vanillin. Both solvents and cations were found to be crucial in the carboxylation of phenoxides. Due to solvation effects, DMSO directs CO₂ attack to the para-position of phenoxide, while DMF, although less selective, generally affords higher HACA yields. The addition of equiv. amounts of mesitolate salt to phenoxide in either DMSO or DMF solution often drives the reaction to completion, resulting in yields of up to 98%. Phenoxides containing several EWG groups, such as halogens or alkyl groups, adjacent to the reaction center show considerably lower reactivity in carboxylation; however, by carefully adjusting parameters, acceptable conversions (>70%) can be achieved. Using the gasometry, we assessed the stability of phenoxide and mesitolate carbonate complexes in DMSO. These experiments revealed distinct stages for the onset of decomposition and carboxylation at atmospheric pressure, indicating a lower energy barrier in the homogeneous process. Further insight into carbonate complex behavior was obtained through DOSY and ¹³C NMR experiments, which support increased molecular association in solution and correlate with enhanced reactivity. Full article

The S11D mining complex in Brazil, situated in Pará state, extracts 20 million tons of iron each quarter. Connecting via a standard 802.11b/g/n wireless network is crucial for mine operations across vast distances. A local team employs a network monitoring tool called the Ekahau Site Survey to guarantee the proper functioning of the network. However, due to the harsh terrain and the dangerous nature of S11D operations, this tool fails to gather data from all points of interest, resulting in interpolated maps that may not accurately represent the network’s overall quality. In this work, we propose a platform that can be attached to mobile machines during operations to automatically collect network parameters, such as channelization, RSSI, latency, packet loss, and bandwidth, without requiring human intervention. Using these network data, we generate an RSSI map using Kriging, which the local team can use. Comparison tests conducted in the laboratory and the field demonstrate that the platform performs similarly to Ekahau in capturing network parameters, ensuring its use in day-to-day operations for mapping. Full article

Three Ir(III) complexes 1–3 were synthesized using phenyl-modified 2-phenylpyridine derivatives as the cyclometalating ligands. All complexes exhibited aggregation-induced phosphorescence emission (AIPE) in CH₃CN/H₂O, which facilitated highly sensitive detection of 2,4,6-trinitrophenol (TNP). Among them, complex 3 containing a phenyl group at the para-position of the phenyl moiety in 2-phenylpyridine showed superior detection performance with the limit of detection (LOD) of 74 nM. 1–3 demonstrated excellent anti-interference and selectivity performances for the detection of TNP in different common water samples. In addition, ¹H NMR spectra, density functional theory calculations, and spectroscopic results indicate that the detection mechanism for TNP is attributed to the combined effects of photo-induced electron transfer and the inner-filter effect. Full article

Urban green spaces (UGS) are pivotal to urban sustainability, yet their morphology—patch size, shape, and configuration—remains insufficiently linked to institutional drivers. We investigate how land tenure strength shapes UGS morphology across 36 cities in nine countries. Using OpenStreetMap data, we delineate UGS and compute landscape metrics (AREA, PARA, SHAPE, FRAC, PAFRAC) via FRAGSTATS; we develop a composite index of land tenure strength capturing ownership, use-right duration, expropriation compensation, and government land governance capacity. Spearman’s rank correlations indicate a scale-dependent coupling: stronger tenure is significantly associated with micro-scale patterns—smaller patch areas and more complex, irregular boundaries—consistent with fragmented ownership and higher transaction costs, whereas macro-scale indicators (e.g., overall green coverage/connectivity) show weaker sensitivity. These findings clarify an institutional pathway through which property rights intensity influences the physical fabric of urban nature. Policy implications are twofold: in high-intensity contexts, flexible instruments (e.g., transferable development rights, negotiated acquisition, ecological compensation) can maintain network connectivity via embedded, fine-grain interventions; in low-intensity contexts, one-off land assembly can efficiently deliver larger, regular green cores. The results provide evidence-based guidance for aligning green infrastructure design with diverse governance regimes and advancing context-sensitive sustainability planning. Full article

V658 Car is the first known eclipsing binary system involving a classical Be star and an sdOB companion, offering a unique opportunity to study disk physics and binary interactions in unprecedented detail. From TESS data and multi-color observations from the comissão para a colaboração entre profissionais e amadores collaboration, we analyze the system’s color–magnitude diagram and compare it with radiative transfer models that include the Be star, its circumstellar disk, and the sdOB companion. While the stellar eclipses are well reproduced, two features observed in the multi-color photometry challenge the current modeling paradigm: the discrepancy between the observed reddening and the modeled blueing during the first attenuation phase and the complete lack of modeled attenuation around the second stellar eclipse. These issues highlight the need for more sophisticated modeling approaches to capture the complex interplay between disk opacity and binary dynamics. Full article

A para-substituted 1,10-phenanthroline ligand, 2-(4-methylphenoxy)-1,10-phenanthroline (L24), was synthesized and structurally characterized. Complexes with Eu³⁺, Tb³⁺, Sm³⁺, and Dy³⁺ were obtained in a 2:1 ligand-to-metal ratio and analyzed using single-crystal x-ray diffraction, photoluminescence spectroscopy, and TD-DFT calculations. Coordination via the phenanthroline nitrogen atoms, combined with steric asymmetry from the para-methylphenoxy group, induces low-symmetry environments favorable for electric-dipole transitions. Excited-state lifetimes reached 2.12 ms (Eu³⁺) and 1.12 ms (Tb³⁺), with quantum yields of 42% and 68%, respectively. The triplet-state energy of L24 (22,741 cm⁻¹) aligns well with emissive levels of Eu³⁺ and Tb³⁺, consistent with Latva’s criterion. Fluorescence titrations indicated positively cooperative complexation, with association constants ranging from 0.60 to 1.67. Stark splitting and high ⁵D₀ → ⁷F₂/⁷F₁ intensity ratios (R₂ = 6.25) confirm the asymmetric coordination field. The para-methylphenoxy substituent appears sufficient to lower coordination symmetry and strengthen electric-dipole transitions, offering a controlled route to enhance photoluminescence in Eu³⁺ and Tb³⁺ complexes. Full article

Schiff base ligands prepared from salicylaldehyde and 2-, 3- and 4-methoxybenzylamine were used to prepare copper(II) complexes, characterized by spectral methods, elemental analysis and X-ray crystallography in the case of complex 4a derived from 2-methoxybenzylamine. The DNA cleavage activity of the prepared complexes was exceptional, with best activities of over 95% one-strand cleavage for 4c at 3 mM and full double-strand cleavage for complex 4a at 5 mM. Absorption titration studies with ct-DNA revealed good binding constants (at 10⁵ M⁻¹) with a decrease of up to 56% light absorption. Meanwhile, the EB–DNA displacement method and viscosity studies revealed groove binding as a possible binding mode. For BSA binding studies, all three complexes showed K_BSA values in the optimal range for reversible BSA binding (10⁴ M⁻¹). The copper(II) complexes showed significant cytotoxic effects (67–96% at 1 mM) in mitochondrial activity monitoring assays. Cytotoxicity was confirmed against cancer cell lines (A549 and HepG2) and HEL cells. The complexes 4a and 4c exhibited high activity against HepG2 cancer cells (IC50 < 22 μM), comparable to cisplatin. The radical scavenging activity was determined by the INT method with the best IC50 for 4c (189 ± 11 μM). Overall, complexes 4a and 4c with a methoxy group in the ortho and para positions show high potential in most determined activities, but mainly as DNA cleavers and as cytotoxic agents with selectivity against HepG2 cells. Full article

In this paper, we aimed to evaluate whether simple, low molecular mass benzoquinone derivatives, featuring different substituents in para- and meta-position relative to the tert-butyl group, possess biological activities against major targets associated with Alzheimer’s disease. The 1,4-benzoquinone derivatives studied herein inhibited both cholinesterases in the micromolar concentration range, generally showing a preference for butyrylcholinesterase over acetylcholinesterase; formed complexes with biometal ions Fe²⁺, Cu²⁺ and Zn²⁺; and displayed a certain BACE1 inhibition. Moreover, the tested compounds displayed certain antioxidant activity via either electron transfer or hydrogen atom transfer mechanisms. The antioxidant capacity of the unsubstituted tert-butyl-1,4-benzoquinone (compound 1) was three times lower than that of the standard antioxidant BHT, while 2,6-disubstituted derivatives (compounds 15 and 7) exhibited peroxyl radical scavenging activity comparable to that of Trolox. Taken together with in silico-predicted low toxicity, good intestinal absorption and favorable oral bioavailability, the presented 1,4-benzoquinone derivatives are promising scaffolds for the design of more complex molecules with enhanced cholinesterase and BACE1 inhibitory activity. Furthermore, they could serve as functional substituents in other structural scaffolds to combine and enhance their biological activities. Full article

Background: The Amazon biome exhibits complex arboviral transmission dynamics influenced by accelerating deforestation, climate change, and socioeconomic inequities. Objectives/Methods: This study integrates official epidemiological records with socioeconomic, environmental, and climate variables by applying advanced geostatistical methods (Moran’s I, SaTScan, kernel density estimation) combined with principal component analysis and negative binomial regression to assess the spatiotemporal dynamics of dengue incidence and its association with socio-environmental determinants across municipalities in Pará state (eastern Brazilian Amazon) from 2010 to 2024. Results: Dengue incidence showed an overall decline but with marked epidemic peaks in 2010–2012, 2016, and 2024. The spatial analysis revealed significant clustering (Moran’s I = 0.221, p < 0.01), with persistent high-risk hotspots across most of Pará. Of 144 municipalities, 104 exhibited significant dengue risk, while 58 maintained sustained transmission. Negative binomial regression model identified key determinants: illiteracy, low urbanization, reduced GDP, and climate variables. Conclusions: Dengue transmission in the Amazon is driven by synergistic socio-environmental disruptions, necessitating intersectoral policies that bridge public health surveillance, sustainable land-use governance, and poverty alleviation. Priority actions include targeted vector control in high-risk clusters, coupled with integrated deforestation and climate monitoring to predict outbreak risks. The findings emphasize the urgency of implementing multisectoral interventions tailored to the territorial and socio-environmental complexities of vulnerable Amazonian regions for effective dengue control. Full article

The natural history of focal non-infected lesions of the abdominal aorta (fl-AA) remains unclear and largely depends on their aetiology. These lesions often involve a focal “tear” or partial disruption of the arterial wall. Penetrating aortic ulcers (PAUs) and intramural hematomas (IMHs) are examples of focal tears in the aortic wall that can either progress to dilatation (saccular aneurysm) or fail to fully propagate through the medial layers, potentially leading to aortic dissection. These conditions typically exhibit a morphology consistent with eccentric saccular aneurysms. The management of focal non-infected pathologies of the abdominal aorta remains a subject of debate. Unlike fusiform abdominal aortic aneurysms, the inconsistent definitions and limited information regarding the natural history of saccular aneurysms (sa-AAAs) have prevented the establishment of universally accepted practice guidelines for their management. As emphasized in the latest 2024 ESVS guidelines, the focal nature of these diseases makes them ideal candidates for endovascular repair (class of evidence IIa—level C). Moreover, the Society for Vascular Surgery just referred to aneurysm diameter as an indication for treatment suggesting using a smaller diameter compared to fusiform aneurysms. Consequently, the management of saccular aneurysms is likely heterogeneous amongst different centres and different operators. Endovascular repair using tube stent grafts offers benefits like reduced recovery times but carries risks of migration and endoleak due to graft rigidity. These complications can influence long-term success. In this context, the use of endovascular bifurcated grafts may provide a more effective solution for treating these focal aortic pathologies. It is essential to achieve optimal sealing regions through anatomical studies of aortic morphology. Additionally, understanding the anatomical characteristics of focal lesions in challenging necks or para-visceral locations is indeed crucial in device choice. Off-the-shelf devices are favoured for their time and cost efficiency, but new endovascular technologies like fenestrated endovascular aneurysm repair (FEVAR) and custom-made devices enhance treatment success and patient safety. These innovations provide stent grafts in various lengths and diameters, accommodating different aortic anatomies and reducing the risk of type III endoleaks. Although complicated PAUs and focal saccular aneurysms rarely arise in the para-visceral aorta, the consequences of rupture in this segment might be extremely severe. Experience borrowed from complex abdominal and thoracoabdominal aneurysm repair demonstrates that fenestrated and branched devices can be deployed safely when anatomical criteria are respected. Elective patients derive the greatest benefit from a fenestrated graft, while urgent cases can be treated confidently with off-the-shelf multibranch systems, reserving other types of repairs for emergent or bail-out cases. While early outcomes of these interventions are promising, it is crucial to acknowledge that limited aortic coverage can still impede effective symptom relief and lead to complications such as aneurysm expansion or rupture. Therefore, further long-term studies are essential to consolidate the technical results and evaluate the durability of various graft options. Full article

The Amazon rainforest hosts a diverse array of forest types, including those where Brazil nut (Bertholletia excelsa) occurs, which plays a crucial ecological and economic role. The Brazil nut is the second most important non-timber forest product in the Amazon, a symbol of development and sustainable use in the region, promoting the conservation of the standing forest. Understanding the vertical structure of these forests is essential to assess their ecological complexity and inform sustainable management strategies. We used terrestrial laser scanning (TLS) to assess the vertical structure of Amazonian forests with the occurrence of Brazil nut (Bertholletia excelsa) at regional (Amazonas, Mato Grosso, Pará, and Amapá) and local scales (forest typologies in Amapá). TLS allowed high-resolution three-dimensional characterization of canopy layers, enabling the extraction of structural metrics such as canopy height, rugosity, and leaf area index (LAI). These metrics were analyzed to quantify the forest vertical complexity and compare structural variability across spatial scales. These findings demonstrate the utility of TLS as a precise tool for quantifying forest structure and highlight the importance of integrating structural data in conservation planning and forest monitoring initiatives involving B. excelsa. Full article