Unforeseen plant phenotypic diversity in a dry and grazed world.

Earth harbours an extraordinary plant phenotypic diversity1 that is at risk from ongoing global changes2,3. However, it remains unknown how increasing aridity and livestock grazing pressure-two major drivers of global change4-6-shape the trait covariation that underlies plant phenotypic diversity1,7. Here we assessed how covariation among 20 chemical and morphological traits responds to aridity and grazing pressure within global drylands. Our analysis involved 133,769 trait measurements spanning 1,347 observations of 301 perennial plant species surveyed across 326 plots from 6 continents. Crossing an aridity threshold of approximately 0.7 (close to the transition between semi-arid and arid zones) led to an unexpected 88% increase in trait diversity. This threshold appeared in the presence of grazers, and moved toward lower aridity levels with increasing grazing pressure. Moreover, 57% of observed trait diversity occurred only in the most arid and grazed drylands, highlighting the phenotypic uniqueness of these extreme environments. Our work indicates that drylands act as a global reservoir of plant phenotypic diversity and challenge the pervasive view that harsh environmental conditions reduce plant trait diversity8-10. They also highlight that many alternative strategies may enable plants to cope with increases in environmental stress induced by climate change and land-use intensification.

Diagnosis and treatment of urethral stricture in men with neurogenic lower urinary tract dysfunction: A systematic review.

AIM: To summarize available data focused on diagnosis and management of urethral stricture in men with neurogenic lower urinary tract dysfunction by a systematic review of the literature. MATERIALS AND METHODS: A systematic review of the literature was carried out through an extensive electronic database search performed in PubMed/MEDLINE and Scopus databases for full texts, and International Continence Society, American Urology Association, and European Association of Urology abstracts for citations related to urethral structure. This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. RESULTS: A total of 316 articles were identified, 48 of which were selected for this review. Different strategies are currently being used for the management of urethral strictures, such as clean intermittent catheterization (CIC) which reduces stricture by up to 68%; direct vision internal urethrotomy which shows lower rates of renarrowing; urethroplasty which shows a success rate up to 70%; urinary diversion is the treatment of choice when reconstruction is not possible. CONCLUSIONS: Further studies are needed in this population because of the heterogeneity of the outcomes and the lack of a standardized definition and classification of this population.

Plant height and hydraulic vulnerability to drought and cold.

Understanding how plants survive drought and cold is increasingly important as plants worldwide experience dieback with drought in moist places and grow taller with warming in cold ones. Crucial in plant climate adaptation are the diameters of water-transporting conduits. Sampling 537 species across climate zones dominated by angiosperms, we find that plant size is unambiguously the main driver of conduit diameter variation. And because taller plants have wider conduits, and wider conduits within species are more vulnerable to conduction-blocking embolisms, taller conspecifics should be more vulnerable than shorter ones, a prediction we confirm with a plantation experiment. As a result, maximum plant size should be short under drought and cold, which cause embolism, or increase if these pressures relax. That conduit diameter and embolism vulnerability are inseparably related to plant size helps explain why factors that interact with conduit diameter, such as drought or warming, are altering plant heights worldwide.

Mapping tree species vulnerability to multiple threats as a guide to restoration and conservation of tropical dry forests.

Understanding the vulnerability of tree species to anthropogenic threats is important for the efficient planning of restoration and conservation efforts. We quantified and compared the effects of future climate change and four current threats (fire, habitat conversion, overgrazing and overexploitation) on the 50 most common tree species of the tropical dry forests of northwestern Peru and southern Ecuador. We used an ensemble modelling approach to predict species distribution ranges, employed freely accessible spatial datasets to map threat exposures, and developed a trait-based scoring approach to estimate species-specific sensitivities, using differentiated trait weights in accordance with their expected importance in determining species sensitivities to specific threats. Species-specific vulnerability maps were constructed from the product of the exposure maps and the sensitivity estimates. We found that all 50 species face considerable threats, with an average of 46% of species' distribution ranges displaying high or very high vulnerability to at least one of the five threats. Our results suggest that current levels of habitat conversion, overexploitation and overgrazing pose larger threats to most of the studied species than climate change. We present a spatially explicit planning strategy for species-specific restoration and conservation actions, proposing management interventions to focus on (a) in situ conservation of tree populations and seed collection for tree planting activities in areas with low vulnerability to climate change and current threats; (b) ex situ conservation or translocation of populations in areas with high climate change vulnerability; and (c) active planting or assisted regeneration in areas under high current threat vulnerability but low climate change vulnerability, provided that interventions are in place to lower threat pressure. We provide an online, user-friendly tool to visualize both the vulnerability maps and the maps indicating priority restoration and conservation actions.

Direct and indirect effects of plant and frugivore diversity on structural and functional components of fruit removal by birds.

Seed dispersal is an important ecosystem function, but it is contentious how structural and functional diversity of plant and bird communities are associated with seed-dispersal functions. We used structural equation models to test how structural (i.e., abundance, species richness) and functional diversity (i.e., functional dispersion and community-weighted means of functional traits) of fruiting plants and frugivorous birds directly and indirectly influence the respective components of fruit removal. We recorded plant and bird diversity in point counts and observed plant-frugivore interactions in a tropical mountain forest in Ecuador. We also recorded plant and bird morphological traits to calculate measures of functional diversity. We found that fruit abundance had a positive direct effect on bird abundance, which directly and indirectly mediated the abundance of removed fruits. Plant and bird species richness were only directly related to the richness of the removed fruits. Functional dispersion of the plant community was positively associated to that of the bird community and to that of the removed fruits. Consistently, we found positive associations between community-weighted means of plant and bird traits and between community-weighted means of plant traits and that of plants with removed fruits. In contrast, community-weighted means of the bird community were unrelated to that of the removed fruits. Overall, our results suggest that plant abundance directly and indirectly influences fruit removal, likely because of avian fruit tracking. However, we did not find strong links between the functional diversity of the frugivore community and removed fruits, suggesting that other factors in addition to plant-animal trait matching might be important for the functional diversity of removed fruits. Our findings highlight the importance of frugivore abundance for maintaining seed dispersal by animals in tropical forests.

Decoupling of soil nutrient cycles as a function of aridity in global drylands.

The biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the twenty-first century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. We find a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems.

Identification of Antibacterial Phenolics in Selected Plant Species from Mexican Cloud Forest by Mass Spectrometry Dereplication.

Fifteen plant species from a protected cloud forest (CF) in Veracruz, Mexico, were screened for their in vitro capacity to inhibit the growth of the phytopathogenic bacteria Chryseobacterium sp., Pseudomonas cichorii, Pectobacterium carotovorum and Pantoea stewartii, causal agents of damage to crops like 'chayote', lettuce, potato and corn. As a result, the bioactivity of Turpinia insignis and Leandra cornoides is reported for the first time against Chryseobacterium sp. and P. cichorii. In addition, 24 and 18 compounds not described for these species were dereplicated by an UPLC/MS-MS method, respectively. The identified compounds included simple phenols, hydroxycinnamic acids, flavonoids and coumarins. The antibacterial assay of 12 of them demonstrated the bacteriostatic effect of vanillin, trans-cinnamic acid, scopoletin and umbelliferone against Chryseobacterium sp. These findings confirm for the first time the value of the CF plants from Veracruz as sources of bioactive natural products with antimicrobial properties against phytopathogenic bacteria.

Pollen Resources Used by Two Species of Stingless Bees (Meliponini) in a Tropical Dry Forest of Southern Ecuador.

Pollinators are crucial for ecosystem functionality; however, little is known about the plant species used by some of these, such as stingless bees. In this study, for the first time, pollen resources used by Melipona mimetica Cockerell (Hymenoptera: Apidae: Meliponini) and Scaptotrigona sp. Moure (Hymenoptera: Apidae: Meliponini) were identified through analysis of corbicular pollen found on worker bees in a dry forest in southern Ecuador. In total, 68 pollen types were identified belonging to 31 botanical families. The most represented plant families were Fabaceae (16%), Malvaceae (7%), and Boraginaceae (7%). Both stingless bee species exhibited a polylectic behavior, with an average of 16 pollen types collected by individual bees. Differences in abundances of pollen types collected by each species indicated distinct uses for these two bee species.

[Endoscopic dilatation in a patient with achalasia during pregnancy: case report and review of the literature]. / Dilatación endoscópica en paciente con acalasia durante el embarazo: reporte de caso y revisión de la literatura.

Achalasia in pregnancy is an infrequent, poorly understood condition and its treatment is not clearly defined. The repercussions on the patients nutritional status are serious and in a pregnant woman have serious implications for the course of gestation, with high risk of intrauterine growth restriction, preterm delivery and even fetal loss; there are symptoms that can be confused with hyperemesis gravidarum delaying the diagnosis. The therapeutic options are medical treatment, endoscopic and surgical interventions; to decide what is the best treatment, we should be taken into account the severity, gestational age and patient conditions. Within the spectrum mentioned in the management include calcium antagonists and nitrates, however these have restrictions in pregnancy, another options are botulinum toxin, endoscopic pneumatic dilation, laparoscopic Heller myotomy and recently POEM. In pregnancy there is a few evidence in the literature and in this moment there are about 40 reported cases, some with complications such as fetal loss and maternal death. We present our experience at the San Ignacio University Hospital in Bogotá, Colombia, with a 26-year-old woman with a novo diagnosis of achalasia type II during the first trimester of pregnancy, with a clinical history of severe dysphagia associated with malnutrition. She was management with enteral nutrition support with nasogastric tube to achieve repletion of the body mass index (BMI) and after that, she had a endoscopic management with Rigiflex balloon dilation. It allowed to successfully carry out pregnancy without adverse effects on the mother or the fetus, with adequate evolution and oral tolerance without dysphagia. We consider that nutritional support is important prior to taking a desicion with this type of patient, in addition that endoscopic management with balloon dilation can be safe and effective for the management of achalasia in pregnancy.

Small-scale topography modulates elevational α-, ß- and γ-diversity of Andean leaf beetles.

Elevational diversity gradients are typically studied without considering the complex small-scale topography of large mountains, which generates habitats of strongly different environmental conditions within the same elevational zones. Here we analyzed the importance of small-scale topography for elevational diversity patterns of hyperdiverse tropical leaf beetles (Coleoptera: Chrysomelidae). We compared patterns of elevational diversity and species composition of beetles in two types of forests (on mountain ridges and in valleys) and analyzed whether differences in the rate of species turnover among forest habitats lead to shifts in patterns of elevational diversity when scaling up from the local study site to the elevational belt level. We sampled beetle assemblages at 36 sites in the Podocarpus National Park, Ecuador, which were equally distributed over two forest habitats and three elevational levels. DNA barcoding and Poisson tree processes modelling were used to delimitate putative species. On average, local leaf beetle diversity showed a clear hump-shaped pattern. However, only diversity in forests on mountain ridges peaked at mid-elevation, while beetle diversity in valleys was similarly high at low- and mid-elevation and only declined at highest elevations. A higher turnover of species assemblages at lower than at mid-elevations caused a shift from a hump-shaped diversity pattern found at the local level to a low-elevation plateau pattern (with similar species numbers at low and mid-elevation) at the elevational belt level. Our study reveals an important role of small-scale topography and spatial scale for the inference on gradients of elevational species diversity.

Clinicopathologic and Surgical Study of Pleomorphic Adenoma of the Parotid Gland: Analysis of Risk Factors for Recurrence and Facial Nerve Dysfunction.

PURPOSE: To determine whether clinicopathologic or surgical features are risk factors for recurrence and facial nerve dysfunction in pleomorphic adenoma (PA) of the parotid gland. PATIENTS AND METHODS: The records of 198 patients surgically treated for a PA of the parotid gland from 1999 through 2013 were retrospectively reviewed to identify patients who developed a tumor recurrence. The Fisher exact test and Mann-Whitney U test were used to analyze patient characteristics between recurrent and non-recurrent PAs. Logistic regression was used to determine the risks of recurrence and facial nerve dysfunction. RESULTS: Twenty-three patients (11.6%) developed a recurrence. Patients with tumor recurrence were notably younger than patients without recurrence. Of the 14 patients who underwent enucleation, 11 (78.6%) developed residual disease, as did 10 of 165 patients (6%) managed by a superficial parotidectomy (P < .0005). Furthermore, the risk of residual disease was 9.3 to 21.6 times higher in patients who underwent enucleation than in those who underwent a total or superficial parotidectomy. For tumor histology, recurrence was observed in 3 (15.8%) of the 19 cellular types, 18 (11.5%) of 157 classic cases, and 1 (4.8%) of 21 myxoid cases (P = .5). The risk of recurrence with positive resection margins was 49 times higher than with negative margins (P = .001). CONCLUSION: Young age, enucleation, and positive margins are risk factors for residual pleomorphic adenoma, and surgical technique and histomorphologic features are associated with increased facial nerve dysfunction.

[Las cardiopatías congénitas en el 2018].

We present an update of the most relevant advances of three-dimensional echocardiography for the diagnosis of congenital heart diseases. The evolution of its treatment is analyzed, showing the results obtained in recent years. The functional and structural changes experienced in women with congenital heart disease during pregnancy are discussed, as well as the main health risks and the importance of teamwork in healthcare to treat these patients. Finally, we provide a review on the current situation in Mexico and outline some improvement recommendations.

Se presenta una actualización de los avances más relevantes de la ecocardiografía tridimensional para el diagnóstico de las cardiopatías congénitas. Se analiza la evolución de su tratamiento y se describen los resultados obtenidos en los últimos años. En el tema de la mujer embarazada con cardiopatía congénita se subrayan los cambios funcionales y estructurales durante el embarazo, así como los riesgos por considerar y la importancia del trabajo en equipo para tratar a estas enfermas. Finalmente se aportan datos de la situación en México y las medidas recomendadas para mejorarla.

Sclerosing Polycystic Adenosis of the Parotid Gland: A Systematic Review and Report of 2 New Cases.

PURPOSE: We sought to evaluate clinical-epidemiologic aspects, pathologic characteristics, and treatment of sclerosing polycystic adenosis (SPA) of the parotid gland and to report 2 new cases. MATERIALS AND METHODS: We conducted a systematic review following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for studies published in or before June 2016. The inclusion criteria were as follows: final diagnosis of SPA affecting the parotid gland and articles published in Spanish or English. The exclusion criteria were as follows: unclear diagnosis after pathologic analysis and patients affected by other conditions in the major salivary glands. We added 2 new cases. RESULTS: Our review ultimately included 21 articles and 45 cases. The mean patient age was 41 years (range, 7-84 years). The female-to-male ratio was 2:1. In all patients the tumor showed progressive growth. The evolution range was 7 days to 11 years. In 17.7% of cases, the tumor was associated with pain. The average tumor size was 30.3 mm (range, 12-60 mm). Fine needle aspiration biopsy (FNAB) was unable to diagnose 30 cases. Benign tumors comprised 58% of tumors (18), whereas malignancy was present in 25.8% (8). Thirty-five tumors were well circumscribed. There were 8 multinodular or lobed cases. The tumor was described as encapsulated in 1 case, partially encapsulated or pseudo-encapsulated in 16, and not encapsulated in 12. Five cases showed different degrees of degenerative changes, ranging from dysplasia to invasive carcinoma. All cases underwent surgical treatment. Superficial parotidectomy with preservation of the facial nerve was performed in 22 cases (61.1%), total parotidectomy in 8 (22.2%), and tumor enucleation in 6 (16.6%). The mean follow-up period was 51.5 months (range, 5-276 months). Of documented cases, 74.2% had 2 or more years of follow-up. Recurrences occurred in 6 cases (16.6%). CONCLUSIONS: We consider SPA a benign tumor with progressive growth, which is occasionally painful. It occurs around age 40 years and occurs more often in female patients. Fine needle aspiration biopsy does not provide an adequate preoperative diagnosis. Recurrences are infrequent. Follow-up should be customized according to the pathologic findings. Malignant transformation may occur. Superficial parotidectomy with facial nerve preservation is the treatment of choice.

An approach to the phenomenology of the disease. / Una aproximación a la fenomenología de la enfermedad.

Modern medicine has undergone technological progress, undoubtedly with better results, but the doctor-patient relationship has been undermined in its most important aspect, human contact. The patient experiences and confronts in solitude his adverse experience. This experience is complex, not only are the symptoms of the disease, they also include disability, isolation, fear, dependence and sometimes guilt. Phenomenology attaches a paramount importance to the data in the consciousness of the patient, as facts given with absolute value. The purpose of this paper is to deepen the experience of the healthy adult individual who is ill. The better understanding of this phenomenology of the patient by the physician and the health personnel, can favor a better efficiency, empathy and compassion in their care.

[Corrected transposition of the great arteries]. / Transposición corregida de las grandes arterias (TCGA), problema no resuelto.

Corrected transposition of the great arteries is one of the most fascinating entities in congenital heart disease. The apparent corrected condition is only temporal. Over time, most patients develop systemic heart failure, even in the absence of associated lesions. With current imaging studies, precise visualization is achieved in each case though the treatment strategy remains unresolved. In asymptomatic patients or cases without associated lesions, focalized follow-up to assess systemic ventricular function and the degree of tricuspid valve regurgitation is important. In cases with normal ventricular function and mild tricuspid failure, it seems unreasonable to intervene surgically. In patients with significant associated lesions, surgery is indicated. In the long term, the traditional approach may not help tricuspid regurgitation and systemic ventricular failure. Anatomical correction is the proposed alternative to ease the right ventricle overload and to restore the systemic left ventricular function. However, this is a prolonged operation and not without risks and long-term complications. In this review the clinical, diagnostic, and therapeutic aspects are overviewed in the light of the most significant and recent literature.

Functional traits determine plant co-occurrence more than environment or evolutionary relatedness in global drylands.

Plant-plant interactions are driven by environmental conditions, evolutionary relationships (ER) and the functional traits of the plants involved. However, studies addressing the relative importance of these drivers are rare, but crucial to improve our predictions of the effects of plant-plant interactions on plant communities and of how they respond to differing environmental conditions. To analyze the relative importance of -and interrelationships among- these factors as drivers of plant-plant interactions, we analyzed perennial plant co-occurrence at 106 dryland plant communities established across rainfall gradients in nine countries. We used structural equation modeling to disentangle the relationships between environmental conditions (aridity and soil fertility), functional traits extracted from the literature, and ER, and to assess their relative importance as drivers of the 929 pairwise plant-plant co-occurrence levels measured. Functional traits, specifically facilitated plants' height and nurse growth form, were of primary importance, and modulated the effect of the environment and ER on plant-plant interactions. Environmental conditions and ER were important mainly for those interactions involving woody and graminoid nurses, respectively. The relative importance of different plant-plant interaction drivers (ER, functional traits, and the environment) varied depending on the region considered, illustrating the difficulty of predicting the outcome of plant-plant interactions at broader spatial scales. In our global-scale study on drylands, plant-plant interactions were more strongly related to functional traits of the species involved than to the environmental variables considered. Thus, moving to a trait-based facilitation/competition approach help to predict that: 1) positive plant-plant interactions are more likely to occur for taller facilitated species in drylands, and 2) plant-plant interactions within woody-dominated ecosystems might be more sensitive to changing environmental conditions than those within grasslands. By providing insights on which species are likely to better perform beneath a given neighbour, our results will also help to succeed in restoration practices involving the use of nurse plants.

[Results of training in the electronic health records in a tertiary care hospital]. / El expediente electrónico: resultados de la capacitación para su uso en un hospital de alta especialidad.

AIM: To assess the user evaluation of the electronic health records system together with its training program and to investigate the relation between the number of training sessions and the corresponding evaluation scores given by the participants. MATERIAL AND METHODS: An anonymous survey was conducted between the medical, nursing and social worker personnel. The survey included seven multiple-choice questions with a numerical scale from 1 to 10 and an additional open question. STATISTICAL ANALYSIS: IBM SPSS Statistics v18 software was used to perform ANOVA variance analysis. RESULTS: In total, 340 workers participated in this study; 317 were included in the statistical analysis, out of which 76% had one or two training sessions, 13.9% received three or more sessions and 10% had no training. The mean global training evaluation by the participants was 5.9 ± 2.3, median 6.3, while the electronic records system evaluation was 5.2 ± 2.3, median 5.5. CONCLUSIONS: In relation to the training and electronic records system it was observed that higher evaluation scores were obtained with increasing number of training sessions (p < 0.001). On the electronic records systems, personnel with no training evaluated the system with a mean score of 3.9 ± 2.7, while those who received three or more training sessions evaluated the system with a mean score of 6.1 ± 1.8 (p < 0.001).

Bacterial Diversity in Old Hydrocarbon Polluted Sediments of Ecuadorian Amazon River Basins.

The Ecuadorian Amazon rainforest stands out as one of the world's most biodiverse regions, yet faces significant threats due to oil extraction activities dating back to the 1970s in the northeastern provinces. This research investigates the environmental and societal consequences of prolonged petroleum exploitation and oil spills in Ecuador's Amazon. Conducted in June 2015, the study involved a comprehensive analysis of freshwater sediment samples from 24 locations in the Rio Aguarico and Napo basins. Parameters such as water and air temperature, conductivity, soil pH, and hydrocarbon concentrations were examined. Total petroleum hydrocarbon (TPH) concentrations ranged from 9.4 to 847.4 mg kg-1, with polycyclic aromatic hydrocarbon (PAH) levels varying from 10.15 to 711.1 mg kg-1. The pristane/phytane ratio indicated historic hydrocarbon pollution in 8 of the 15 chemically analyzed sediments. Using non-culturable techniques (Illumina), bacterial analyses identified over 350 ASV, with prominent families including Comamonadaceae, Chitinophagaceae, Anaeromyxobacteraceae, Sphingomonadaceae, and Xanthobacteraceae. Bacterial diversity, assessed in eight samples, exhibited a positive correlation with PAH concentrations. The study provides insights into how microbial communities respond to varying levels of hydrocarbon pollution, shedding light on the enduring impact of oil exploitation in the Amazonian region. Its objective is to deepen our understanding of the environmental and human well-being in the affected area, underscoring the pressing need for remedial actions in the face of ongoing ecological challenges.

Woody plant taxonomic, functional, and phylogenetic diversity decrease along elevational gradients in Andean tropical montane forests: Environmental filtering and arrival of temperate taxa.

Mountains are paramount for exploring biodiversity patterns due to the mosaic of topographies and climates encompassed over short distances. Biodiversity research has traditionally focused on taxonomic diversity when investigating changes along elevational gradients, but other facets should be considered. For first time, we simultaneously assessed elevational trends in taxonomic, functional, and phylogenetic diversity of woody plants in Andean tropical montane forests and explored their underlying ecological and evolutionary causes. This investigation covered four transects (traversing ca. 2200 m a.s.l.) encompassing 114 plots of 0.1 ha across a broad latitudinal range (ca. 10°). Using Hill numbers to quantify abundance-based diversity among 37,869 individuals we observed a consistent decrease in taxonomic, functional, and phylogenetic diversity as elevation increased, although the decrease was less pronounced for higher Hill orders. The exception was a slight increase in phylogenetic diversity when dominant species were over-weighted. The decrease in taxonomic and functional diversity might be attributed to an environmental filtering process towards highlands, where the increasingly harsher conditions exclude species and functional strategies. Besides, the differences in steepness decrease between Hill orders suggest that rare species disproportionately contribute to functional diversity. For phylogenetic diversity the shifting elevational trend between Hill orders indicates a greater than previously considered influence in central Andean highlands of tropical lowlands originated species with strong niche conservatism relative to distantly related temperate lineages. This could be explained by a decreasing presence and abundance of temperate, extratropical taxa towards the central Andes relative to northern or southern Andes, where they are more prevalent.

Flow Behavior through Porous Media and Displacement Performance of a SILICA/PAM Nanohybrid: Experimental and Numerical Simulation Study.

Nanoparticles (NPs) have been proposed as additives to improve the rheological properties of polymer solutions and reduce mechanical degradation. This study presents the results of the retention experiment and the numerical simulation of the displacement efficiency of a SiO2/hydrolyzed polyacrylamide (HPAM) nanohybrid (CSNH-AC). The CSNH-AC was obtained from SiO2 NPs (synthesized by the Stöber method) chemically modified with HPAM chains. Attenuated total reflection-Fourier transform infrared spectroscopy, field emission gun-scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis were used to characterize the nanohybrid. The injectivity and dynamic retention tests were performed at 56 °C in a sandstone core with a porosity of ∼26% and a permeability of 117 and 287 mD. A history matching of the dynamic retention test was performed to determine the maximum and residual adsorption, IPV, and residual resistance factor (RRF). A laboratory-scale model was used to evaluate the displacement efficiency of CSNH-AC and HPAM through numerical simulation. According to the results, the nanohybrid exhibits better rheological behavior than the HPAM solution at a lower concentration. The nanopolymer sol adsorption and IPV (29,7 µg/grock, 14,5) are greater than those of the HPAM solution (9,2 µg/grock, 10), which was attributed to the difference between the rock permeabilities used in the laboratory tests (HPAM: 287 mD and CSNH-AC: 117 mD). The RF of both samples gradually increases with the increase in shear rate, while the RRF slightly decreases and tends to balance. However, the nanopolymer sol exhibits greater RF and RRF values than that of the polymer solution due to the strong flow resistance of the nanohybrid (higher retention in the porous media). According to the field-scale simulation, the incremental oil production could be 295,505 and 174,465 barrels for the nanopolymer sol and the HPAM solution, respectively (compared to waterflooding). This will represent an incremental recovery factor of 11.3% for the nanopolymer sol and 6.7% for the HPAM solution.