The energy sector is currently undergoing a rapid transformation with the integration of power electronic converter (PEC)-interfaced renewable energy sources (RES), such as wind and solar ...photovoltaic (PV) systems, at both the transmission and distribution networks. Power system stability has been significantly influenced by this power grid transformation. This paper comprehensively reviews major power system stability issues affected due to large-scale integration of PEC-interfaced RES in power grids, with some example case studies relevant for each stability category. According to the review, stability issues are mainly originating from reduction in synchronous inertia, reduction in reactive power reserve, low short-circuit strength of the power network, and fault ride-through (FRT) strategy/capability of the PEC-interfaced RES. Decrease in synchronous inertia could affect both the rotor angle stability and the frequency stability, while decrease in short-circuit strength and reactive power reserve could cause voltage stability and rotor angle stability issues in power networks. Sub-synchronous control interactions are also receiving a lot of attention by the power industry due to increasing oscillatory stability incidents reported in power networks with PEC-interfaced RES. FRT capabilities/strategies of PEC-interfaced RES are also playing a pivotal role in power grid stability due to its influence on active and reactive power, hence more emphasis should be placed on FRT schemes of PEC-interfaced RES, since future power grids are expected to operate with 100% PEC-interfaced generation sources. Stability improvement strategies could be implemented to address multiple stability issues in PEC-interfaced power networks; however, rigorous stability studies are required to identify the optimal conditions to implement these improvement strategies. Furthermore, ongoing structural changes in power grids to accommodate remotely sited PEC-interfaced RES are also influencing the stability of power grids. Therefore, all these factors must be carefully considered by system operators when planning and operating power grids in a secure and stable manner with high penetration levels of PEC-interfaced RES.
Background Non-alcoholic fatty liver disease (NAFLD) is a common liver disease. The aim of the present study was to explore the relation of visfatin with underlying histopathological changes of NAFLD ...patients. Subjects A population of 55 NAFLD patients was analyzed in a cross-sectional study. A liver biopsy was realized. Weight, basal glucose, insulin, insulin resistance (HOMA), total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, and visfatin levels were measured. A bioimpedance was performed. Results and conclusions The mean age was 42.8 ± 11.2 years, the mean BMI was 33.1 ± 10.2 with 37 males (67.3%) and 18 females (32.7%). Probabilities to have; portal inflammation increased 1.11 (CI95%:1.03-1.50) with each increment of 1 ng/ml of visfatin concentration, high grade of steatosis increased 1.25 (CI 95%:1.06-1.61) with each unit of insulin concentrations, fibrosis increased 1.12 (CI 95%:1.02-1.43) with each unit of fat mass and lobulillar inflammation increased 13.4 (CI 95%:1.3-147) with each unit of HOMA-IR. Portal inflammation frequencies were different between groups (low visfatin group 13.07 < ng/ml: 37.5% versus high visfatin group 13.07 > ng/ml: 62.5%; P < 0.05). In conclusion, several histopathological changes in liver biopsies could be explained by insulin concentrations, HOMA-IR, and fat mass amount. Moreover, visfatin plasma concentrations could predict the presence of portal inflammation in NAFLD patients.
The outcome of 45 neonates with EEG-confirmed seizures (ESz) was analyzed with regard to treatment. ESz persisted in 17 of 32 neonates receiving phenobarbital/phenytoin (13 had a poor outcome, 4 ...died). In contrast, ESz were rapidly controlled in 13 of 13 nonresponders to phenobarbital/phenytoin treated with midazolam (4 had poor outcome, 2 died). Nonresponders to phenobarbital/phenytoin had a significantly worse outcome than responders did. Midazolam effectively controlled ESz in nonresponders to phenobarbital/phenytoin and correlated with significantly improved long-term neurodevelopment.
Due to their excellent surface properties, gold nanoparticles have been used in a wide range of applications from optics and catalysis to biology and cancer treatment by thermal therapy. Gold ...nanoparticles can absorb a large amount of radiation according to their geometry, such as nanospheres and nanorods. The importance of gold nanoparticles geometry is based on the electromagnetic spectrum wavelength where exists a greater absorption of radiation, which belongs to the visible region for nanospheres and ranges between visible and near infrared regions for nanorods, conferring greater biomedical applicability to the latter. When using photochemical synthesis method, which consists of reducing gold atoms to their metallic state with UV radiation, the geometry of gold nanoparticles depends on different variables such as: 1) pH, 2) concentration of chloroauric acid, 3) the surfactant, 4) concentration of silver nitrate, 5) temperature and 6) irradiation time. Therefore, in this study the geometry of the gold nanoparticles obtained by photochemical synthesis was determined as a function of solution pH and chloroauric acid concentration, using Spectrophotometry in the Ultraviolet Visible region (UV-vis) as characterization technique. From the analysis of the UV-vis spectra, it was determined that at an acidic pH the particles have two absorption bands corresponding to nanorods geometry, while at a basic pH only nanospheres are found and at a neutral pH the lower relative intensity of the second band indicates the simultaneous existence of the two geometries. The increase in the concentration of chloroauric acid produces a decrease in the amount of synthesized nanorods, seen as a decrease of the relative intensity of the second absorption band. Therefore, obtaining gold nanoparticles with nanorods geometry favours fields such as biomedicine, because they are capable of absorbing infrared radiation and can be used as photosensitive agents in localized thermal therapy against cancer.
In vitro studies on the structurally related mycosporine-like amino acids (MAAs) porphyra-334 and shinorine in aqueous solutions were carried out aiming at their full photochemical and photophysical ...characterization and expanding the evidence on the assigned UV-photoprotective role of the molecules in vivo. The experiments on shinorine confirmed a high photostability and a poor fluorescence quantum yield, in concordance with previous results on porphyra-334. The estimation of triplet production quantum yields for both MAAs was achieved by laser-flash photolysis measurements. In particular, photosensitization experiments on porphyra-334 support the participation of the triplet state in the photodecomposition mechanism yielding a more precise value of capital Phi(T). As well, photoacoustic calorimetry experiments allowed the first direct quantification of the nonradiative relaxation pathways of the excited MAAs in solution, corroborating that the vast majority (ca. 97%) of the absorbed energy is promptly delivered to the surroundings as heat, consistently with the low photodecomposition and emission yields observed.
This work quantifies the evolution in the implementation and development of renewable energies in Colombia, as well as evidence the current challenges and development prospects. The high demand for ...electricity in Colombia is increasing due to the great increase in population, industry and commerce, which generates greater energy consumption and as a consequence economic, social and environmental problems. The objective of this study was to analyze the behavior of the energy projects submitted to the Mining Energy Planning Group (UPME) during the last 15 years until July 2022, as well as to study the research areas with the highest performance. technology and the corresponding radiation intensity. In addition, it shows an historic information about the projects presented both not in force as of the date of closing of this investigation, classified according to their source, according to their range of power and according to its stage of implementation, finally, we made a synthesis of the new regulations governing the motivation and implementation of projects with renewable energy sources, being as this work a very good source of reference for further studies of the implementation of renewable energy sources in Colombia.
The nature and origin of cosmic rays remains one of the greatest puzzles of modern astrophysics after more than 50 years since their first registration. Several ground experiments have reported the ...rate registered at its height of operation. To continue with the study of cosmic rays, we propose obtain the rate at different heights in the Earth's atmosphere, developing a small and portable ultraviolet radiation detector, consisting of a scintillation plastic, a PMT, and a fast DAQ system. In this work we present the design and construction of the UV detector and the rate recorded in the Sierra Negra Volcano near Puebla, Mexico (4200 m.a.s.l).
We evaluated spray-dried animal plasma (SDAP) as an alternative to antimicrobial medication with colistin sulfate in weanling pigs challenged with Escherichia coli K99. Forty-eight piglets weaned at ...24 d of age were distributed into 12 pens, and each pen was assigned to one of four dietary treatments. All the piglets were given an oral dose of 5 × 10(7) cfu of E. coli K99 at weaning. The dietary treatments followed a factorial arrangement with two levels of SDAP (0 and 7%) and two levels of colistin (0 and 300 mg/kg of diet). The ADG and ADFI were measured on d 7 and 14 of trial. Three piglets from each treatment were killed on d 7 and 14 to remove the small intestine, and to obtain ileal and cecal digestive contents. The inclusion of SDAP improved ADG by 68 g (P < 0.05) and ADFI by 41 g (P < 0.10) in wk 1 of trial. During wk 2, SDAP improved ADG by 41 g (P < 0.10) and gain:feed ratio (G:F) by 25% (P < 0.01). On the other hand, whereas colistin had no effect on performance in wk 1, it improved ADG by 102 g (P < 0.01), ADFI by 62 g (P < 0.01), and G:F by 26% (P < 0.01) in wk 2. Over the 14 d of the trial, ADG was improved by 54 (P < 0.05) and 75 g (P < 0.05), and G:F was improved by 35 (P < 0.05) and 32% (P < 0.05) due to SDAP and colistin, respectively. There was interaction between colistin and SDAP for ADFI in wk 2 and between d 0 to 14 (P < 0.05), which indicates that their effects were not additive. The use of colistin was advantageous in the maintenance of the integrity of the intestinal mucosa of the pigs, as suggested by a small intestine that was 93 g heavier (P < 0.10) and with the tallest villi 106 μm longer (P < 0.10) than in pigs without colistin. The inclusion of SDAP in the diet favored the growth of lactobacilli in the ileum (P < 0.10) and the cecum (P < 0.05), whereas colistin reduced the number of enterococci in the cecum (P < 0.05) and of Escherichia coli both in the ileum and the cecum (P < 0.001). These results suggest that SDAP may be an alternative to medicated feed with antibiotics since it provided a level of protection against an experimental challenge with E. coli K99 similar to that obtained with colistin, an antibiotic of proven efficacy. The current situation in which the use of antimicrobials in animal feeding is being questioned should encourage further investigation into the use of SDAP as a means of preventing disease in pigs at weaning.
Highlights • The mechanism of association among socio-demographics, spirituality, and QoL remains vague. • Financial circumstances QoL is compromised among older adults. • Institutionalization in a ...nursing home positively and negative affects spirituality and QoL. • Spirituality has direct positive and negative effects on QoL dimensions. • A model of the interaction of an elderly’s socio-demographics, spirituality, and QoL is proposed.
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