The effect of fluvial avulsion on the Holocene chronostratigraphic record and the agricultural signal of the world's largest coastal lagoonal system.

This study identified the occurrence of Holocene chronology hiatuses in the sedimentary record of the Patos-Mirim system caused by river avulsion processes, as well as evidence of sharp anthropogenic changes in the surrounding region of the lagoon water bodies. The presence of chronology hiatuses demonstrates the importance of considering the disturbance effect of paleo-drainage processes on the paleoenvironmental resolution and expression of the sedimentary record of such coastal plains. Anthropogenic activities especially those related to agriculture and forestry have increased significantly during the great acceleration, resulting in modifications of both the landscape and the environmental conditions of the lagoon bodies. Such impacts were clearly reflected in the sedimentary record where abrupt changes in palynological trends, sedimentary DNA, isotopic and granulometric analyses were inferred. The climatic conditions combined with regressive sea level can explain the chronology hiatuses. Pollen analyses demonstrated changes in the landscape, particularly indicated by the shift from Cyperaceae to Poaceae dominance after the 1960 CE. Therefore, all proxies together demonstrate the modification in the landscape and changes in the environment, clearly influenced by anthropogenic action from unsustainable agricultural practices.

Accurate internal cavities and kissing bond sizing in metal plates by using the time-of-flight of laser-induced ultrasound waves.

This paper presents a nondestructive method for accurately identifying internal flaws in metal plates, which is crucial for ensuring structural integrity in safety-critical applications. The technique relies on analyzing laser-induced ultrasound (LIU) longitudinal wave time-of-flight, as demonstrated through a theoretical five-layer model. Experimental validation was conducted using a piezo-sensor in contact with a slab containing millimetric artificial cavities immersed in air, resulting in a discrepancy of 5.05%. In contrast, experiments performed in a water medium exhibited a lower discrepancy of 2.5%. (Discrepancy refers to differences between measurements obtained through an experimental time-of-flight analysis and caliper measurements.) The results obtained in water-based experiments affirm the accuracy of the proposed model. B-scan measurements and the five-layer model were utilized to generate 2D reconstructed images, enabling precise localization and sizing of cavities and kissing bonds between plates, finding an average size of kissing bond of 30 µm. In conclusion, the proposed five-layer model, based on a longitudinal wave time-of-flight analysis, provides a straightforward framework for an easy cavity and kissing bond measurements in metal plates.

Extended states in random dimer gated graphene superlattices.

Ordered and disordered semiconductor superlattices represent structures with completely opposed properties. For instance, ordered superlattices exhibit extended Bloch-like states, while disordered superlattices present localized states. These characteristics lead to higher conductance in ordered superlattices compared to disordered ones. Surprisingly, disordered dimer superlattices, which consist of two types of quantum wells with one type always appearing in pairs, exhibit extended states. The percentage of dissimilar wells does not need to be large to have extended states. Furthermore, the conductance is intermediate between ordered and disordered superlattices. In this work, we explore disordered dimer superlattices in graphene. We calculate the transmission and transport properties using the transfer matrix method and the Landauer-Büttiker formalism, respectively. We identify and discuss the main energy regions where the conductance of random dimer superlattices in graphene is intermediate to that of ordered and disordered superlattices. We also analyze the resonant energies of the double quantum well cavity and the electronic structure of the host gated graphene superlattice (GGSL), finding that the coupling between the resonant energies and the superlattice energy minibands gives rise to the extended states in random dimer GGSLs.

Gaussian and Gaussian-pulsed-like Fermi velocity graphene structures.

Gaussian and Gaussian-related structures are quite attractive due to its versatility to modulate the electronic transport, including its possibility as electron filters. Here, we show that these non-conventional profiles are not the exception when dealing with Fermi velocity barriers in monolayer graphene. In particular, we show that Gaussian Fermi velocity graphene barriers (G-FVGBs) and Gaussian-pulsed-like Fermi velocity graphene superlattices (GPL-FVGSLs) can serve as electron band-pass filters and oscillating conductance structures. We reach this conclusion by theoretically studying the transmission and transport properties of the mentioned structures. The study is based on the continuum model, the transfer matrix method and the Landauer-Büttiker formalism. We find nearly flat transmission bands or pass bands for G-FVGBs modulable through the system parameters. The pass bands improve as the maximum ratio of Fermi velocities (ξmax) increases, however its omnidirectional range is reduced. These characteristics result in a decaying conductance (integrated transmission) withξmax. The integrated transmission remains practically unaltered with the size of the system due to the saturation of the electron pass band filtering. In the case of GPL-FVGSLs the GPL profile results in regions of high transmission probability that can merge as flat transmission minibands if the pulse fraction and the superlattice parameters are appropriately tuned. The GPL profile also results in conductance (integrated transmission) oscillations that can be multiplied or reduced in number by adjusting the pulse fraction as well as the superlattice parameters.

The influence of Amazon River connectivity to littoral meanders on long-term carbon accumulation: A case study of Lake Yahuarcaca.

The objective of this investigation is to evaluate the recent changes in the accumulation of organic matter and carbon on the Yahuarcaca lake system, by means of a multiproxy paleolimnological study. The methodology based on lithological descriptions of 210Pb/137Cs-dated cores allowed us to infer the centennial sedimentation processes and carbon accumulation rates. Sedimentary facies, grain size, magnetic susceptibility, loss on ignition, carbonate, chlorophyll derivatives, stable isotopes of δ13C/δ15N, and carbon accumulation rate were analyzed. LANDSAT and photographic record of satellite images were used to reconstruct the historical geomorphological evolution of the Lake. Sediment cores yielded basal ages of 1827 and 1828 Common Era, representing the formation of lakes as a consequence of the Amazon meandering process. Two main paleolimnological stages were identified, with a boundary transition set at 1980-1984 Common Era, attributed to the geomorphological closure and complete lake separation from the Amazon and the onset of full lentic conditions. This inference was mainly based on both sharp increases in the sedimentation rate from 0.2 to >1 cm yr-1 and carbon accumulation that increased seven-fold (from 2 to 14 g m-2 yr-1) from 1980 to 1984 Common Era. The flood-pulse and connection to the Amazon defined the magnitude of organic inputs, where areas more distant/isolated from the river showed higher accumulation of carbon from autochthonous production, with an average of 8.9 % and 1.10 g m-2 yr-1 (carbon accumulation rate). Those areas closer and connected to the river were strongly related to the interannual hydrological variability, with a lower mean carbon content (5.9 %) and 0.73 g m-2 yr-1 (carbon accumulation rate). We concluded that carbon burial was highest within the most distant spot from the Amazon River because of the weaker connection to the river itself and the more stable lentic conditions for net sedimentation.

The use of microplastics as a reliable chronological marker of the Anthropocene onset in Southeastern South America.

Microplastics (MPs) represent an emergent contamination marker. For this reason, we analyzed the vertical distribution of MPs in six sediment cores retrieved from the Patos-Mirim System, the world's largest coastal lagoonal system. The sediment cores span from mid Holocene to present times according to both radiocarbon and lead dating and are located close to both urban/industrial and agricultural regions. We identified a basal pre-disturbance MP-free zone in all cores and an uppermost contaminated 70-cm-zone, where a general increasing trend in MPs content resembling the human anthropization process was recorded. The predominant format of MPs was fiber, followed by fragments. The most commonly identified polymers were rayon, PVC, acrylate, polycarbonate and cellophane. Urban/industrial and agricultural activities were shown as clear sources of MPs, leading to comparable MPs concentration values in the sediment cores. Thus, MPs are collectively a reliable indicator of the Anthropocene onset, and in the Patos-Mirim System the most appropriate chronology can be assigned to the beginning of 1970s, matching the intensification of anthropogenic activities in the area.

The effect of agricultural intensification and water-locking on the world's largest coastal lagoonal system.

The palaeolimnological conditions of Mirim Lagoon, a large coastal shallow lagoon under the influence of historical human impacts related to the development of the primary sector of the economy were reconstructed. The first significant human impact consisted of locking the estuarine system to induce the transition from brackish to freshwater conditions. During this transition, the sedimentation rate consistently increased from pre-disturbance values of 0.25 cm yr-1 to >1 cm yr-1. A concomitant increase in nitrogen and carbon values was recorded indicating a related eutrophication process. The highest nutrient levels were achieved during the 1990s after the incorporation of cutting-edge technologies for agricultural production such as high-yielding varieties of rice resistant to climate variability and pests, and the use of inorganic fertilisers, pesticides and water supply controlled by irrigation. After 2011, the soybean production boosted and the area cultivated with this oilseed equalled the area of rice paddies, i.e., 2 × 105 ha. A sharp decrease in δ13C from -19 to -24‰ and in δ15N from 6 to 2‰ were observed in the sedimentary record, indicating a major shift in the composition of the organic matter after the agricultural intensification. Trace elements Cr, Cu, Ni and Zn showed a high positive correlation with Al and Fe, and enrichment factors near 1, indicating a natural and terrigenous source of these elements and also unpolluted conditions. However, the increase of As after 1990 and the positive correlation with Pb was associated with agricultural practices. All elemental ratios (K/Al, Ti/Al and V/Cr) showed constant pre-disturbance trends and a turning point ca. the 1990s. Microplastics were detected from the beginning of the 1990s and increased towards recent sediments, thus corroborating an anthropogenically impacted scenario. Therefore, the development of the primary sector of the economy exerted clear impacts on the environmental quality of the system.

Centennial glacier retreat increases sedimentation and eutrophication in Subantarctic periglacial lakes: A study case of Lake Uruguay.

High resolution XRF scanning documented inter-annual paleolimnological changes of a Subantarctic periglacial lake, during a process of centennial glacier retreat in King George Island, Antarctica. Two major paleoenvironmental stages were inferred from the combined analysis of elemental, molecular and isotopic biomarkers, with a boundary or transition set at about 3200 yr BP. The first stage was characterized by a relatively low allochthonous organic content, reduced productivity and nitrogen levels. Such paleoenvironmental conditions are interpreted as a terrestrial system under periglacial influence, where material influx was related to erosion process from the melt water discharge, because of the proximity to the Collins Glacier ice cap. After the major Holocene glacier advance dated at about 3500 yr BP, the ice cap retreat led to the formation of Lake Uruguay, which involved in filling processes leading to moraine deposits, proglacial meltwater channels, and lakes next to the land glacier. During the second stage, with the onset of the Current Warm Period, prior to 1900 CE the stabilization of the Zr/Rb ratio within the laminated sediments documented the origin of the lacustrine sedimentation system, with subsequent increases in the sedimentation rate and biomass content (total nitrogen and organic carbon). Time series analyses revealed that the lake displayed variability cycles related to El Niño Southern Oscillation (ENSO), as reflected by high resolution sedimentological proxies for grain size, weathering, allochthonous inputs from the watershed, increase of biomass and productivity, and changes in redox conditions, all of which displayed similar oscillation cycles from 2 to 6 yr. During this periglacial recession and associated eutrophication process, we detected a striking loss in both bacterial specific richness and diversity as inferred from preliminary selected ancient DNA analyses. Thus, the Antarctic warming scenario leading to glacier depletion appears to exert deterioration consequences on the Subantarctic microbial web.

Anthropogenic and natural variability in the composition of sedimentary organic matter of the urbanised coastal zone of Montevideo (Río de la Plata).

This study is aimed to identify the different sources of sedimentary organic matter (SOM) within Montevideo coastal zone (MCZ). To this end δ13C, δ15N and C/N ratio were analysed in surface sediments and a sediment core. Sediment core analysis showed that until ~1950CE SOM was mainly marine, observing a shift towards lower δ13C in recent sediments, evidencing an estuarine composition. This trend was associated to the climatic variability, which exerted a major influence on the SOM composition, leading to an increased input of terrigenous material and associated anthropogenic contaminants. Surface sediments collected during different El Niño South Oscillation (ENSO) phases did not show inter-annual variability in SOM composition, which was mainly marine in both eastern and western region of MCZ and estuarine in Montevideo Bay. This spatial pattern provides new insights on the dynamics and factors affecting organic matter sources available for primary consumers along the study region.

Historical economic and environmental policies influencing trace metal inputs in Montevideo Bay, Río de la Plata.

Montevideo Bay is located in the middle zone of the Rio de la Plata, and since the foundation of the city, several key economic and environmental policies affected the industry, and thus, metal inputs into this ecosystem. The aim of this study is to evaluate the sedimentary geochemical record of Montevideo Bay, in order to determine the historical inputs of anthropogenic metals to the system. In addition, environmental and economic policies of the country were taken into account to infer the relationship between them and the historic metal input. Concentrations of aluminum, chromium, copper, lead, scandium and zinc were analyzed and the EF and SPI indices were calculated. The analysis showed that since Montevideo foundation, metal concentrations increased in accordance with industry development, and the indices as well as the metal concentration represent a reliable footprint of the history of different economic and environmental policies influencing historical industrial activities.

Assessing the ecological quality status of a temperate urban estuary by means of benthic biotic indices.

Benthic indices are commonly used tools for assessing the environmental quality, because they represent a simple source of scientific information. However, their performance could vary depending on the application area and perturbation types, thus they should be tested before used in other remote geographic regions. This study aims to test the use of some of the most widely common benthic biotic indices for assessing the environmental quality of Montevideo's coastal zone at a seasonal scale against many physicochemical variables. From all the evaluated indices, AMBI appears to be the most suitable one to assess the environmental quality. The study also allowed us to infer the most relevant physicochemical variables: protein, lipid and heavy metal sediment concentration. Additionally, site-specific threshold effect levels for heavy metals and biopolymers were established, which appear to be useful to determine tolerable levels of such stressors in future assessments or monitoring programs for the study area.

Competition drives clumpy species coexistence in estuarine phytoplankton.

Understanding the mechanisms that maintain biodiversity is a fundamental problem in ecology. Competition is thought to reduce diversity, but hundreds of microbial aquatic primary producers species coexist and compete for a few essential resources (e.g., nutrients and light). Here, we show that resource competition is a plausible mechanism for explaining clumpy distribution on individual species volume (a proxy for the niche) of estuarine phytoplankton communities ranging from North America to South America and Europe, supporting the Emergent Neutrality hypothesis. Furthermore, such a clumpy distribution was also observed throughout the Holocene in diatoms from a sediment core. A Lotka-Volterra competition model predicted position in the niche axis and functional affiliation of dominant species within and among clumps. Results support the coexistence of functionally equivalent species in ecosystems and indicate that resource competition may be a key process to shape the size structure of estuarine phytoplankton, which in turn drives ecosystem functioning.

Malaria grave por Plasmodium falciparum / Severe malaria due to plasmodium falciparum

No disponible

Efecto terapéutico de Mitomicina C en el postoperatorio inmediato de pacientes con tumores vesicales no músculo invasores de bajo riesgo / Therapeutic effect of mitomycin C in the immediate postoperatory in patients with low-risk non-muscle-invasive bladder tumours

Introducción: El cáncer vesical es una de las enfermedades con más alta prevalencia entre los distintos tipos de neoplasia debido a su tendencia a la recidiva. El tratamiento en las etapas iniciales es la resección transuretral (RTU). Sin embargo, después de la RTU de un tumor vesical no músculo invasor, un porcentaje alto recidivarán en 1-2 años. Por esta razón, se ha propuesto la administración de quimioterapia o inmunoterapia adyuvante después de la RTU en un intento de disminuir la recidiva y prevenir la progresión. Pacientes y métodos: Estudio prospectivo, controlado y randomizado. Se incluyeron 100 pacientes con tumores vesicales no músculo-invasores de bajo riesgo. Todos los pacientes sometidos inicialmente a RTU y posteriormente randomizados para recibir Mitomicina C (MMC) postoperatoria en dosis única. Resultados: Todos los tumores eran menores de 3 cm. La media de seguimiento fue de 26,43 ± 7,65 meses. Se administró MMC en 49 pacientes, de los cuales el 67,3% no recidivó y el 32,7% lo hicieron como tumor vesical no invasor. Delos 51 pacientes que no recibieron MMC, el 51% no recidivaron, el 47% recidivaron como tumor no invasor y el 2% como tumor invasor. Se encontraron diferencias significativas en cuanto al tiempo libre de enfermedad según se empleara MMC postoperatoria o nada. Conclusiones: Cuando evaluamos a los pacientes con carcinoma vesical no músculo invasor de bajo riesgo, pertenecientes a un solo centro sanitario y con dosis alta de MMC en dosis única tras la RTU, evidenciamos un mayor tiempo libre de enfermedad estadísticamente significativa frente a los casos en los que no se utilizó ningún tratamiento (AU)

Introductión: Bladder cancer is a disease with a high prevalence due to its recurrence rate. Transurethral resection of the bladder (TURB) is the treatment in initial stages. Nevertheless, a high percentage of non-muscle-invasive tumors treated will have a recurrence 1-2 years afterwards. Adjuvant quemotherapy or immunotherapy after TURB has been administered in order to decrease the rate of recurrence and to prevent progression. Patients and methods: A prospectived, controlled and randomized study was performed. We included 100 patients with non-muscle-invasive and bladder tumors the low grade. All patients had initially a TURB performed and were randomized to either receive or not a single dose mitomycin C (MMC) in the immediate postoperatory. Results: All low grade tumors was less than 3 cm. Mean follow-up was 26,43±7,65 months. MMC was administered in 49 patients, of these, 67,3% had no recurrence and 32,7% had a non-muscle-invasive recurrence. Of the 51 patients in the non mitomycin, 51% had no recurrence while 47% had a non-muscle-invasive recurrence, and 2% had a muscle invasive progression. We found significantly differences in time to recurrence among the two groups. Summary: We found a greater time to recurrence in the group of single dose adjuvant MMC being this difference statistically significantly when comparing with the other group (AU)

Frecuencia de complicaciones perinatales en pacientes con trastorno por déficit de la atención e hiperactividad, otras enfermedades psiquiátricas infantiles y sujetos sanos / Frequency of perinatal complications in patients with attention deficit hyperactivity disorder, other childhood psychiatric disorders and healthy subjects

FUNDAMENTO: Se ha propuesto que en el origen del trastorno por déficit de la atención e hiperactividad (TDAH) se encuentra implicada la interacción de factores genéticos y ambientales. Entre estos últimos, se han considerado las complicaciones durante el embarazo y el parto como probables factores de riesgo asociados al TDAH. PACIENTES Y MÉTODO: Se valoraron la historia perinatal y los antecedentes heredofamiliares de ambos padres biológicos de un grupo de pacientes con un rango de edad de 4 a 17 años diagnosticados por medio de la entrevista estructurada MINI-KID como TDAH puros (n = 18), TDAH comórbido con diversas enfermedades (n = 26), pacientes con otras afecciones diferentes al TDAH (n = 28) y controles sanos (n = 18). RESULTADOS: Se observó una mayor frecuencia de complicaciones durante el parto, como rotura prematura de membranas, trabajo de parto prolongado, circular de cordón y la aplicación de la maniobra de Kristeller en pacientes con TDAH comórbido y con otras enfermedades en comparación con los sujetos sanos. Adicionalmente, se observó una mayor frecuencia de antecedentes heredofamiliares de enfermedades psiquiátricas en los 3 grupos de pacientes en comparación con los controles sanos. Al controlar el efecto de estas variables entre sí se observó que los antecedentes psiquiátricos heredofamiliares ejercían una mayor influencia que las complicaciones natales. CONCLUSIONES: La interacción entre las complicaciones natales y los antecedentes psiquiátricos heredofamiliares tiene un efecto considerable en el origen del TDAH y en otras enfermedades diferentes a ésta (AU)

Characterization of the Sinorhizobium meliloti genes encoding a functional dihydrodipicolinate synthase (dapA) and dihydrodipicolinate reductase (dapB).

In bacteria, the known pathways for diaminopimelate (DAP) and lysine biosynthesis share two key enzymes, dihydrodipicolinate synthase and dihydrodipicolinate reductase, encoded by the dapA and dapB genes, respectively. In rhizobia, these genes have not yet been genetically characterized. In this work, by sequence analysis, we identified two divergent open reading frames on the 140-MDa plasmid pRmeGR4b of Sinorhizobium meliloti strain GR4. Termed dapA and dapB, these encode products which show significant sequence similarities to DapA and DapB proteins, respectively. Escherichia coli DAP auxotrophs (dapA and dapB mutants) could be complemented with the pRmeGR4b dapA and dapB genes, indicating that these genes code for functional dihydrodipicolinate synthase and dihydrodipicolinate reductase, respectively. Reverse-transcriptase PCR analyses and beta-galactosidase assays using transcriptional dapA-lacZ and dapB-lacZ fusions suggest that these genes are constitutively expressed in S. meliloti. The dapA and dapB genes are not widely distributed in S. meliloti and appear to be specific for strains carrying pRmeGR4b-type plasmids.

Sinorhizobium meliloti nfe (nodulation formation efficiency) genes exhibit temporal and spatial expression patterns similar to those of genes involved in symbiotic nitrogen fixation.

The nfe genes (nfeA, nfeB, and nfeD) are involved in the nodulation efficiency and competitiveness of the Sinorhizobium meliloti strain GR4 on alfalfa roots. The nfeA and nfeB genes are preceded by functional nif consensus sequences and NifA binding motifs. Here, we determined the temporal and spatial expression patterns of the nfe genes in symbiosis with alfalfa. Translational fusions of the nfe promoters with the gusA gene and reverse transcription-polymerase chain reaction analyses indicate that they are expressed and translated within mature nitrogen-fixing nodules and not during early steps of nodule development. Within the nodules the three nfe genes exhibit a spatial expression pattern similar to that of genes involved in symbiotic nitrogen fixation. We show that nfeB and nfeD genes are expressed not only from their own promoters but also from the upstream nfe promoter sequences. Furthermore, with the use of specific antibodies the NfeB and NfeD proteins were detected within the root nodule bacteroid fraction. Finally, NfeB was inmunolocalized in the bacteroid cell membrane whereas NfeD was detected in the bacteroid cytoplasm.