Showing papers by "Simón Bolívar University published in 2020"

Estimating strength properties of geopolymer self-compacting concrete using machine learning techniques

Abstract: There has been a persistent drive for sustainable development in the concrete industry While there are series of encouraging experimental research outputs, yet the research field requires a standard framework for the material development In this study, the strength characteristics of geopolymer self-compacting concrete made by addition of mineral admixtures, have been modelled with both genetic programming (GEP) and the artificial neural networks (ANN) techniques The study adopts a 12M sodium hydroxide and sodium silicate alkaline solution of ratio to fly ash at 033 for geopolymer reaction In addition to the conventional material (river sand), fly ash was partially replaced with silica fume and granulated blast furnace slag Various properties of the concrete, filler ability and passing ability of fresh mixtures, and compressive, split-tensile and flexural strength of hardened concrete were determined The model development involved using raw materials and fresh mix properties as predictors, and strength properties as response Results shows that the use of the admixtures enhanced both the fresh and hardened properties of the concrete Both GEP and ANN methods exhibited good prediction of the experimental data, with minimal errors However, GEP models can be preferred as simple equations are developed from the process, while ANN is only a predictor

Endophytic microorganisms for biocontrol of the phytopathogenic fungus Botrytis cinerea

Abstract: Botrytis cinerea is the most widely studied necrotrophic phytopathogenic fungus. It causes economic losses that are difficult to calculate due to the large number of hosts. While there are a wide array of fungicides on the market to control this phytopathogen, they are not considered sustainable in terms of the environment and human health. The search for new alternatives to control this phytopathogen has led to the use of endophytic microorganisms as biological control agents. Endophytic bacteria and endophytic fungi have been isolated from different plant species and some have proven effective in inhibiting B. cinerea. Furthermore, a significant number of fungistatic or fungicidal metabolites which could be used as alternative complementary chemical controls have been isolated from these fungi and bacteria. In this review, in addition to the metabolites which have shown fungicide activity against this phytopathogen, the different genera and species of endophytic bacteria and fungi are also considered. These have been isolated from various plant species and have displayed antagonistic activity against B. cinerea.

Non-native mollusks throughout South America: emergent patterns in an understudied continent

Abstract: Non-native species have been introduced at escalating rates during the last decades, mainly due to the dispersion generated by the increasing trade and transport worldwide. Mollusks, the second largest metazoan phylum in terms of species richness, are no exception to this pattern, but, to date, a comprehensive synthesis of non-native mollusk species (NNMS) in South America was not available. For this purpose, an e-discussion group was formed with malacologists and taxonomists from South America, where we exchanged and analyzed bibliography, databases and information about NNMS, providing expert opinion to this assessment. The first list of non-native mollusk species for South America, considering terrestrial, freshwater and marine environments, includes 86 NNMS distributed in 152 ecoregions (terrestrial, freshwater and marine) of the 189 recognized for the South American continent. Information on their native region, vectors, first record for South America and distribution, are also provided. In the analysis of the distribution of the NNMS and the entry points of each species (e.g., ports, cargo and passenger airports, cities) and status of conservation of the ecoregions, four hot spots were recognized: Subtropical-Atlantic, Northern Andes, Central Andes and Southern Andes. This work, thus, sets the baseline on NNMS for South America, a key piece of information regarding the development of policies targeting the management of biological invasions and their socio-ecological impacts.

Microbiota and diabetes mellitus: Role of lipid mediators

Abstract: Diabetes Mellitus (DM) is an inflammatory clinical entity with different mechanisms involved in its physiopathology. Among these, the dysfunction of the gut microbiota stands out. Currently, it is understood that lipid products derived from the gut microbiota are capable of interacting with cells from the immune system and have an immunomodulatory effect. In the presence of dysbiosis, the concentration of lipopolysaccharides (LPS) increases, favoring damage to the intestinal barrier. Furthermore, a pro-inflammatory environment prevails, and a state of insulin resistance and hyperglycemia is present. Conversely, during eubiosis, the production of short-chain fatty acids (SCFA) is fundamental for the maintenance of the integrity of the intestinal barrier as well as for immunogenic tolerance and appetite/satiety perception, leading to a protective effect. Additionally, it has been demonstrated that alterations or dysregulation of the gut microbiota can be reversed by modifying the eating habits of the patients or with the administration of prebiotics, probiotics, and symbiotics. Similarly, different studies have demonstrated that drugs like Metformin are capable of modifying the composition of the gut microbiota, promoting changes in the biosynthesis of LPS, and the metabolism of SCFA.

Evaluation of hospital disaster preparedness by a multi-criteria decision making approach: The case of Turkish hospitals

Abstract: Considering the unexpected emergence of natural and man-made disasters over the world and Turkey, the importance of preparedness of hospitals, which are the first reference points for people to get healthcare services, becomes clear. Determining the level of disaster preparedness of hospitals is an important and necessary issue. This is because identifying hospitals with low level of preparedness is crucial for disaster preparedness planning. In this study, a hybrid fuzzy decision making model was proposed to evaluate the disaster preparedness of hospitals. This model was developed using fuzzy analytic hierarchy process (FAHP)-fuzzy decision making trial and evaluation laboratory (FDEMATEL)-technique for order preference by similarity to ideal solutions (TOPSIS) techniques and aimed to determine a ranking for hospital disaster preparedness. FAHP is used to determine weights of six main criteria (including hospital buildings, equipment, communication, transportation, personnel, flexibility) and a total of thirty-six sub-criteria regarding disaster preparedness. At the same time, FDEMATEL is applied to uncover the interdependence between criteria and sub-criteria. Finally, TOPSIS is used to obtain ranking of hospitals. To provide inputs for TOPSIS implementation, some key performance indicators are established and related data is gathered by the aid of experts from the assessed hospitals. A case study considering 4 hospitals from the Turkish healthcare sector was used to demonstrate the proposed approach. The results evidenced that Personnel is the most important factor (global weight = 0.280) when evaluating the hospital preparedness while Flexibility has the greatest prominence (c + r = 23.09).

Residual alignment and its effect on weld strength in material-extrusion 3D-printing of polylactic acid

Abstract: Gaining a molecular understanding of material extrusion (MatEx) 3D printing is crucial to predicting and controlling part properties. Here we report the direct observation of distinct birefringence localised to the weld regions between the printed filaments, indicating the presence of molecular orientation that is absent from the bulk of the filament. The value of birefringence at the weld increases at higher prints speeds and lower nozzle temperatures, and is found to be detrimental to the weld strength measured by tensile testing perpendicular to the print direction. We employ a molecularly-aware non-isothermal model of the MatEx flow and cooling process to predict the degree of alignment trapped in the weld at the glass transition. We find that the predicted residual alignment factor, A ¯ , is linearly related to the extent of birefringence, Δn. Thus, by combining experiments and molecular modelling, we show that weld strength is not limited by inter-diffusion, as commonly expected, but instead by the configuration of the entangled polymer network. We adapt the classic molecular interpretation of glassy polymer fracture to explain how the measured weld strength decreases with increasing print speed and decreasing nozzle temperature.

A network analysis of research productivity by country, discipline, and wealth.

Abstract: Introduction Research productivity has been linked to a country's intellectual and economic wealth. Further analysis is needed to assess the association between the distribution of research across disciplines and the economic status of countries. Methods By using 55 years of data, spanning 1962 to 2017, of Elsevier publications across a large set of research disciplines and countries globally, this manuscript explores the relationship and evolution of relative research productivity across different disciplines through a network analysis. It also explores the associations of those with economic productivity categories, as measured by the World Bank economic classification. Additional analysis of discipline similarities is possible by exploring the cross-country evolution of those disciplines. Results Results show similarities in the relative importance of research disciplines among most high-income countries, with larger idiosyncrasies appearing among the remaining countries. This group of high-income countries shows similarities in the dynamics of the relative distribution of research productivity over time, forming a stable research productivity cluster. Lower income countries form smaller, more independent and evolving clusters, and differ significantly from each other and from higher income countries in the relative importance of their research emphases. Country-based similarities in research productivity profiles also appear to be influenced by geographical proximity. Conclusions This new form of analyses of research productivity, and its relation to economic status, reveals novel insights to the dynamics of the economic and research structure of countries. This allows for a deeper understanding of the role a country's research structure may play in shaping its economy, and also identification of benchmark resource allocations across disciplines for developing countries.

No implementation without cultural adaptation: a process for culturally adapting low-intensity psychological interventions in humanitarian settings.

Abstract: Despite the widely recognised importance of cultural adaptation to increase the effectiveness of psychological interventions, there is little guidance on its process. Developed based on existing theory, we applied a four-step process to culturally adapt a low-intensity psychological intervention for use in humanitarian settings. The four-step process was applied to adapt a WHO low-intensity psychological intervention (i.e. Problem Management Plus, or PM+) for use with displaced Venezuelans and Colombians in Colombia. First, a rapid desk review was used as an (1) information gathering tool to identify local population characteristics. Next, the results were taken forward for the (2) formulation of adaptation hypotheses, whereby PM+ protocols were screened to identify components for adaptation, drawing on the Ecological Validity Model. Third, the elements flagged for adaptation were taken forward for (3) local consultation to firstly, verify the components identified for adaptation, to identify other areas in need of adaptation, and thirdly, to adapt the intervention protocols. Finally, the adapted intervention protocols were reviewed through (4) external evaluations with local experts. The information gathering phase yielded key information on the socioeconomic aspects of the groups targeted for intervention, the availability and need for mental health and psychosocial support, and existing barriers to accessing care. The adaptation hypotheses phase further identified the need for clearer explanations of key concepts, the need for sensitive topics to match local attitudes (e.g., domestic violence, thoughts of suicide), and the identification of culturally appropriate social supports. Building on these first two phases, local consultation subsequently resulted in revised PM+ protocols. The adapted protocols differed from the original format in their focus on the problems unique to these population groups, the way that psychological distress is expressed in this context, and the inclusion of locally available supports. The results of the external evaluation supported the adaptations made to the protocols. The proposed four-step process offers a useful guide for how to adapt low-intensity psychological intervention within humanitarian settings. Despite some limitations, we show that even when time and resources are scarce it is possible and necessary to culturally adapt psychological interventions. We invite further testing, replication, and improvements to this methodology.

Chronic Joint Pain 3 Years after Chikungunya Virus Infection Largely Characterized by Relapsing-remitting Symptoms

Abstract: Objective To determine the frequency of chronic joint pain and stiffness 3 years after infection with chikungunya virus in a Latin American cohort. Methods A cross-sectional follow-up of 120 patients from an initial cohort of 500 patients who reported joint pain 2 years after infection from the Atlantico Department, Colombia. Patients were clinically diagnosed as having chikungunya virus during the 2014–2015 epidemic, and baseline and follow-up symptoms at 40 months were evaluated in serologically confirmed cases. Results Of the initial 500 patients enrolled in the study, 482 had serologically confirmed chikungunya infection. From this group, 123 patients reported joint pain 20 months after infection, and 54% of those patients reported continued joint pain 40 months after infection. Therefore, 1 out of every 8 people who tested serologically positive for chikungunya infection had persistent joint pain 3 years after infection. Participants that followed up in-person were predominantly adult (mean ± SD age 51 ± 14 years) and female (86%). The most common type of pain reported in these patients at 40 months post-infection was pain with periods of relief and subsequent reoccurrence, and over 75% reported stiffness after immobility, with 39% experiencing morning stiffness. Conclusion This is the first report to describe persistent joint pain and stiffness 40 months after viral infection. The high frequency of chronic disease highlights the need to develop prevention and treatment methods. Further studies should be conducted to understand the similarities between post-chikungunya joint pain and rheumatoid arthritis.

Mechanical and durability properties of recycled aggregate concrete with ternary binder system and optimized mix proportion

Abstract: This study aimed to investigate the mechanical and durability properties of recycled aggregate concrete with a ternary binder system and optimized mix proportion. Two concrete batches were developed using a densified mix design approach (DMDA) to evaluate the required mix proportions. Batch I have GGBS content varied at 0%, 10%, 20%, 30%, 40% and 50% at constant w/b ratio of 0.45, while batch II concrete mix have varied water/binder ratios: 0.3, 0.35, 0.4, 0.45 and 0.5 at constant GGBS replacement level of 30%. The fine aggregate (river sand) of the two batches was blended with fly ash at optimum loose packing density (FA + Sand) and superplasticizer (SP) was incorporated in the mix at a constant level of 1.4%. A control mix comprising of natural aggregate was also developed. The results obtained showcased the feasibility of producing structural concrete with recycled aggregates using GGBS and fly ash. The mechanical and durability properties were best at 30% GGBS content and 0.35 water/binder ratio. The DMDA for mix proportion adopted for RAC contributed significantly to improving its properties when compared to NAC, especially at the optimum observed RAC mix with compressive strength of 52 MPa. Also, the mix demonstrated good permeability resistance in terms of chloride-ion ingress and capillary water absorption.

Latitudinal patterns of species diversity on South American rocky shores: Local processes lead to contrasting trends in regional and local species diversity

Abstract: Aim We evaluated whether patterns of species diversity (α, β and γ) of rocky shore assemblages followed latitudinal gradients (i.e. LDGs) along the South American coasts, and tested hypotheses related to potential processes sustaining or disrupting the expected LDG pattern at various spatial scales. Location Coasts of South America. Taxon Macroalgae and sessile/slow‐moving macrofauna on intertidal rocky shores. Methods We evaluated changes in species composition across 143 sites. The degree of replacement and loss of species at different spatial scales (i.e. coasts, regions and sites) were estimated to help distinguish among ecological, historical and evolutionary hypotheses for explaining LDGs. Furthermore, components of diversity and taxonomic distinctness were measured, and variability in these measures was decomposed using analysis of covariance. Finally, we examined relationships between diversity and a suite of environmental and anthropogenic variables to identify potential mechanisms that may be responsible for the reported spatial relationships. Results Species composition varied with latitude, and this variability was relatively consistent on both coasts. At all spatial scales, replacement of species was the dominant phenomenon (>95%), rather than loss in the total number of species ( Main conclusions Species diversity of South American rocky shores followed, with interruptions, LDGs. The trend of those LDGs, however, depended on the scale and metric used to describe diversity. It is proposed that patterns of LDGs at various scales are not the result of a single overarching process but are strongly influenced by local and regional pro cesses. Although the most evident environmental gradient was the decrease in SST towards the south, it was demonstrated that regional and local environmental variables were also important for understanding the increase in regional β‐diversity towards the tropics.

Neprilysin: A Potential Therapeutic Target of Arterial Hypertension?

Abstract: Arterial hypertension is the most prevalent chronic disease in the adult population of developed countries and it constitutes a significant risk factor in the development of cardiovascular disease, contributing to the emergence of many comorbidities, among which heart failure excels, a clinical syndrome that nowadays represents a major health problem with uncountable hospitalizations and the indolent course of which progressively worsens until quality of life decreases and lastly death occurs prematurely. In the light of this growing menace, each day more efforts are invested in the field of cardiovascular pharmacology, searching for new therapeutic options that allow us to modulate the physiological systems that appear among these pathologies. Therefore, in the later years, the study of natriuretic peptides has become so relevant, which mediate beneficial effects at the cardiovascular level such as diuresis, natriuresis, and decreasing cardiac remodeling; their metabolism is mediated by neprilysin, a metalloproteinase, widely expressed in the human and capable of catalyzing many substrates. The modulation of these functions has been studied by decades, giving room to Sacubitril, the first neprilysin inhibitor, which in conjunction with an angiotensin receptor blocker has provided a high efficacy and tolerability among patients with heart failure, for whom it has already been approved and recommended. Nonetheless, in the matter of arterial hypertension, significant findings have arisen that demonstrate the potential role that it will play among the pharmacological alternatives in the upcoming years.

Learning First-Order Symbolic Representations for Planning from the Structure of the State Space.

Abstract: One of the main obstacles for developing flexible AI systems is the split between data-based learners and model-based solvers. Solvers such as classical planners are very flexible and can deal with a variety of problem instances and goals but require first-order symbolic models. Data-based learners, on the other hand, are robust but do not produce such representations. In this work we address this split by showing how the first-order symbolic representations that are used by planners can be learned from non-symbolic inputs that encode the structure of the state space. The representation learning problem is formulated as the problem of inferring planning instances over a common but unknown first-order domain that account for the structure of the observed state space. This means to infer a complete first-order representation (i.e. general action schemas, relational symbols, and objects) that explains the observed state space structures. The inference problem is cast as a two-level combinatorial search where the outer level searches for values of a small set of hyperparameters and the inner level, solved via SAT, searches for a first-order symbolic model. The framework is shown to produce general and correct first-order representations for standard problems like Gripper, Blocksworld, and Hanoi from input graphs that encode the flat state-space structure of a single instance.

Collective Effervescence, Self-Transcendence, and Gender Differences in Social Well-Being During 8 March Demonstrations

Abstract: 8 March (8M), now known as International Women's Day, is a day for feminist claims where demonstrations are organized in over 150 countries, with the participation of millions of women all around the world. These demonstrations can be viewed as collective rituals and thus focus attention on the processes that facilitate different psychosocial effects. This work aims to explore the mechanisms (i.e., behavioral and attentional synchrony, perceived emotional synchrony, and positive and transcendent emotions) involved in participation in the demonstrations of 8 March 2020, collective and ritualized feminist actions, and their correlates associated with personal well-being (i.e., affective well-being and beliefs of personal growth) and collective well-being (i.e., social integration variables: situated identity, solidarity and fusion), collective efficacy and collective growth, and behavioral intention to support the fight for women's rights. To this end, a cross-cultural study was conducted with the participation of 2,854 people (age 18-79; M = 30.55; SD = 11.66) from countries in Latin America (Mexico, Chile, Argentina, Brazil, Peru, Colombia, and Ecuador) and Europe (Spain and Portugal), with a retrospective correlational cross-sectional design and a convenience sample. Participants were divided between demonstration participants (n = 1,271; 94.0% female) and non-demonstrators or followers who monitored participants through the media and social networks (n = 1,583; 75.87% female). Compared with non-demonstrators and with males, female and non-binary gender respondents had greater scores in mechanisms and criterion variables. Further random-effects model meta-analyses revealed that the perceived emotional synchrony was consistently associated with more proximal mechanisms, as well as with criterion variables. Finally, sequential moderation analyses showed that proposed mechanisms successfully mediated the effects of participation on every criterion variable. These results indicate that participation in 8M marches and demonstrations can be analyzed through the literature on collective rituals. As such, collective participation implies positive outcomes both individually and collectively, which are further reinforced through key psychological mechanisms, in line with a Durkheimian approach to collective rituals.

Differential equation for the flow rate of discharging silos based on energy balance

Abstract: Since the early work of Hagen [G. H. L. Hagen, Ber. Verhandl. K. Preuss. Akad. Wiss. Berlin 17, 35 (1852)] and Beverloo et al. [W. Beverloo et al., Chem. Eng. Sci. 15, 260 (1961)CESCAC0009-250910.1016/0009-2509(61)85030-6], the flow rate of granular material discharging through a circular orifice from a silo has been described by means of dimensional analysis and experimental fits and explained through the free-fall arch model. Here, in contrast to the traditional approach, we derive a differential equation based on the energy balance of the system. This equation is consistent with the well-known Beverloo rule due to a compensation of energy terms. Moreover, this equation can be used to explore different conditions for silo discharges. In particular, we show how the effect of friction on the flow rate can be predicted. The theory is validated using discrete element method simulations.

Anti-Aging Effect of Metformin: A Molecular and Therapeutical Perspective.

Abstract: Aging is a time-dependent inevitable process, in which cellular homeostasis is affected, which has an impact on tissue function. This represents a risk factor for the development of numerous non-transmissible diseases. In consequence, the scientific community continues to search for therapeutic measures capable of improving quality of life and delaying cellular aging. At the center of this research is metformin, a widely used drug in Type 2 Diabetes Mellitus treatment that has a reduced adverse effects profile. Furthermore, there is evidence that this drug has beneficial health effects that go beyond its anti-hyperglycemic properties. Among these effects, its geronto-protection capability stands out. There is growing evidence that points out to an increased life expectancy as well as the quality of life in model organisms treated with metformin. Therefore, there is an abundance of research centered on elucidating the mechanism through which metformin has its anti-aging effects. Among these, the AMPK, mTORC1, SIRT1, FOXO, NF.kB, and DICER1 pathways can be mentioned. Furthermore, studies have highlighted the possibility of a role for the gut microbiome in these processes. The next step is the design of clinical essays that have as a goal evaluating the efficacy and safety of metformin as an anti-aging drug in humans to create a paradigm in the medical horizon. The question being if metformin is, in fact, the new antiaging therapy in humans?

Electrochemical Sensor Based on Prussian Blue Electrochemically Deposited at ZrO2 Doped Carbon Nanotubes Glassy Carbon Modified Electrode.

Abstract: In this work, a new hydrogen peroxide (H2O2) electrochemical sensor was fabricated. Prussian blue (PB) was electrodeposited on a glassy carbon (GC) electrode modified with zirconia doped functionalized carbon nanotubes (ZrO2-fCNTs), (PB/ZrO2-fCNTs/GC). The morphology and structure of the nanostructured system were characterized by scanning and transmission electron microscopy (TEM), atomic force microscopy (AFM), specific surface area, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman and Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties were studied by cyclic voltammetry (CV) and chronoamperometry (CA). Zirconia nanocrystallites (6.6 ± 1.8 nm) with cubic crystal structure were directly synthesized on the fCNTs walls, obtaining a well dispersed distribution with a high surface area. The experimental results indicate that the ZrO2-fCNTs nanostructured system exhibits good electrochemical properties and could be tunable by enhancing the modification conditions and method of synthesis. The fabricated sensor could be used to efficiently detect H2O2, presenting a good linear relationship between the H2O2 concentration and the peak current, with quantification limit (LQ) of the 10.91 μmol·L-1 and detection limit (LD) of 3.5913 μmol·L-1.

Synthesis of Silver Nanoparticles Using Aqueous Leaf Extract of Mimosa albida (Mimosoideae): Characterization and Antioxidant Activity.

Abstract: The search for sensitive and rapid analytical techniques for the determination of natural antioxidants is an area in constant growth due, among other aspects, to the complexity of plant matrices. In this study, silver nanoparticles prepared with the aqueous extract of Mimosa albida leaves were used to assess their polyphenolic content and antioxidant capacity. Silver nanoparticles were characterized by different techniques. As a result, nanoparticles of 6.5 ± 3.1 nm were obtained. The total phenolic content in the extract was 1320.4 ± 17.6 mg of gallic acid equivalents GAE· 100 g−1 and in the nanoparticles 257.3 ± 5.1 mg GAE· 100 g−1. From the phenolic profile analyzed by ultra high-performance liquid chromatography (UPLC) with a diode-array detector (DAD), the presence of apigenin and luteolin in the plant extract is postulated. The antioxidant capacity measured by oxygen radical absorbance capacity ORAC-fluorescein assay was 86917 ± 6287 and 7563 ± 967 µmol ET g−1 in the extract and nanoparticles respectively. Electrochemical analysis by cyclic voltammetry (CV) confirmed the effective reduction capacity of the Mimosa albida leaves extract to reduce Ag ions to AgNPs and differential pulse voltammetry (DPV) suggested the presence of two main reducing agents in the extract. From this study, it was concluded that the aqueous extract of Mimosa albida contains reducing agents capable of synthesizing silver nanoparticles, which can be used in the phytochemical industry.

Epicardial Adipose Tissue, Adiponectin and Leptin: A Potential Source of Cardiovascular Risk in Chronic Kidney Disease.

Abstract: The importance of cardiometabolic factors in the inception and progression of atherosclerotic cardiovascular disease is increasingly being recognized. Beyond diabetes mellitus and metabolic syndrome, other factors may be responsible in patients with chronic kidney disease (CKD) for the high prevalence of cardiovascular disease, which is estimated to be 5- to 20-fold higher than in the general population. Although undefined uremic toxins are often blamed for part of the increased risk, visceral adipose tissue, and in particular epicardial adipose tissue (EAT), have been the focus of intense research in the past two decades. In fact, several lines of evidence suggest their involvement in atherosclerosis development and its complications. EAT may promote atherosclerosis through paracrine and endocrine pathways exerted via the secretion of adipocytokines such as adiponectin and leptin. In this article we review the current knowledge of the impact of EAT on cardiovascular outcomes in the general population and in patients with CKD. Special reference will be made to adiponectin and leptin as possible mediators of the increased cardiovascular risk linked with EAT.

Determination of stability constants of ternary copper(II) complexes formed with picolinic acid and several amino acids

Abstract: In this work, the formation of ternary complexes with their respective formation constants in the systems formed by copper (II), picolinic acid and the amino acids = histidine (His), aspartic acid ...