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An original kinetic model is proposed for the direct production of light olefins by hydrogenation of CO2/CO (COx) mixtures over an In2O3-ZrO2/SAPO-34 tandem catalyst, quantifying deactivation by coke. The reaction network comprises 12 individual reactions, and deactivation is quantified with expressions dependent on the concentration of methanol (as coke precursor) and H2O and H2 (as agents attenuating coke formation). The experimental results were obtained in a fixed-bed reactor under the following conditions: In2O3-ZrO2/SAPO-34 mass ratio, 0/1-1/0; 350-425 °C; 20-50 bar; H2/COx ratio, 1-3; CO2/COx ratio, 0-1; space time, 0-10 gIn2O3-ZrO2 h molC-1, 0-20 gSAPO-34 h molC-1; time, up to 500 h; H2O and CH3OH in the feed, up to 5% vol. The utility of the model for further scale-up studies is demonstrated by its application in optimizing the process variables (temperature, pressure, and CO2/COx ratio). The model predicts an olefin yield higher than 7% (selectivity above 60%), a COx conversion of 12% and a CO2 conversion of 16% at 415 °C and 50 bar, for a CO2/COx = 0.5 in the feed. Additionally, an analysis of the effect of In2O3-ZrO2 and SAPO-34 loading in the configuration of the tandem catalyst is conducted, yielding 17% olefins and complete conversion of CO2 under full water removal conditions.
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The automotive sector is demanding higher specifications to achieve maximum efficiency; in this sense a new generation of lubricants with higher thermo-oxidative stability and superior tribological properties is being explored. The formulation of nanolubricants based on the nature of different nanomaterials is one of the most recent approaches, with several gaps to cover, such as dispersion stability, related to the compatibility of proposed nanomaterials with conventional additives and baseoils used in lubricant formulation. This study evaluated the effect of ZnO nanomaterial dispersed in a commercial engine oil using two different approaches; the use of surfactant and nanomaterial surface functionalization to promote higher stability and lower cluster size. Experimental evidence shows a synergetic effect between the tribological protection mechanism and the antioxidant properties in the lubricant. The effect of nanoparticle cluster size, functionalization level, and nanomaterial content are presented.
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Flow boiling is a complex process but very efficient for thermal management in different sectors; enhancing flow boiling heat transfer properties is a research field of great interest. This study proposes the use of various nanomaterials, carbon-based materials, and metal oxides; in n-pentane as a hydrocarbon-based refrigerant to enhance the flow boiling heat transfer coefficient. This thermal property has been experimentally evaluated using a vertical evaporation device of glass with an internal diameter of 20 mm. The results have shown that proposed nanomaterials dispersion in n-pentane has a limited effect on the thermophysical properties and is conditioned by their dispersibility but promotes a significant increment of pentane heat transfer coefficient (h), increasing the overall heat transfer coefficient (U) of the evaporator. The enhanced heat transfer performance is attributed to the behavior of nanoparticles under working conditions and their interaction with the working surface, promoting a higher generation of nucleation sites. The observed behavior suggests a heat transfer mechanism transition from forced convection to nucleate heat transfer, supported by visual observations.
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Long-chain polyunsaturated fatty acids (PUFAs) are prone to nonenzymatic oxidation in response to differing environmental stressors and endogenous cellular sources. There is increasing evidence that phospholipids containing oxidized PUFA acyl chains control the inflammatory response. However, the underlying mechanism(s) of action by which oxidized PUFAs exert their functional effects remain unclear. Herein, we tested the hypothesis that replacement of 1-palmitoyl-2-arachidonyl-phosphatidylcholine (PAPC) with oxidized 1-palmitoyl-2-arachidonyl-phosphatidylcholine (oxPAPC) regulates membrane architecture. Specifically, with solid-state 2H NMR of biomimetic membranes, we investigated how substituting oxPAPC for PAPC modulates the molecular organization of liquid-ordered (Lo) domains. 2H NMR spectra for bilayer mixtures of 1,2-dipalmitoylphosphatidylcholine-d62 (an analog of DPPC deuterated throughout sn-1 and -2 chains) and cholesterol to which PAPC or oxPAPC was added revealed that replacing PAPC with oxPAPC disrupted molecular organization, indicating that oxPAPC does not mix favorably in a tightly packed Lo phase. Furthermore, unlike PAPC, adding oxPAPC stabilized 1,2-dipalmitoylphosphatidylcholine-d6-rich/cholesterol-rich Lo domains formed in mixtures with 1,2-dioleoylphosphatidylcholine while decreasing the molecular order within 1,2-dioleoylphosphatidylcholine-rich liquid-disordered regions of the membrane. Collectively, these results suggest a mechanism in which oxPAPC stabilizes Lo domains-by disordering the surrounding liquid-disordered region. Changes in the structure, and thereby functionality, of Lo domains may underly regulation of plasma membrane-based inflammatory signaling by oxPAPC.
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Ácidos Graxos Insaturados , Membranas Artificiais , Fosfatidilcolinas , Fosfatidilcolinas/química , Ácidos Graxos Insaturados/químicaRESUMO
We have developed a novel molecular design that enables six-electron redox activity in fused phenazine-based organic scaffolds. Combined electrochemical and spectroscopic tests successfully confirm the two-step 6e- redox mechanism. This work offers an opportunity for achieving energy-dense redox flow batteries, on condition that the solubility and stability issues are addressed.
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Fontes de Energia Elétrica , Elétrons , Oxirredução , SolubilidadeRESUMO
The conditions for promoting the joint conversion of CO2 and syngas in the direct synthesis of light olefins have been studied. In addition, given the relevance for the viability of the process, the stability of the In2O3-ZrO2/SAPO-34 (InZr/S34) catalyst has also been pursued. The CO+CO2 (CO x ) hydrogenation experimental runs were conducted in a packed bed isothermal reactor under the following conditions: 375-425 °C; 20-40 bar; space time, 1.25-20 gcatalyst h molC -1; H2/(CO x ) ratio in the feed, 1-3; CO2/(CO x ) ratio in the feed, 0.5; time on stream (TOS), up to 24 h. Analyzing the reaction indices (CO2 and CO x conversions, yield and selectivity of olefins and paraffins, and stability), the following have been established as suitable conditions: 400 °C, 30 bar, 5-10 gcat h molC -1, CO2/CO x = 0.5, and H2/CO x = 3. Under these conditions, the catalyst is stable (after an initial period of deactivation by coke), and olefin yield and selectivity surpass 4 and 70%, respectively, with light paraffins as byproducts. Produced olefin yields follow propylene > ethylene > butenes. The conditions of the process (low pressure and low H2/CO x ratio) may facilitate the integration of sustainable H2 production with PEM electrolyzers and the covalorization of CO2 and syngas obtained from biomass.
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The dynamics of the retained species on ZSM-5 and SAPO-18 catalysts are studied by using a combination of temperature-programmed desorption/oxidation, ex situ analysis, and in situ FTIR spectroscopic measurements over the entire conversion range, using fixed-bed and spectroscopic cell reactors, in continuous and discontinuous mode. The results point to the appropriateness of the combined methodologies to track the interconversion of active into deactivating species. A statistically relevant (supported by linear regression and multivariate analysis) association of the observations is found by using the different complementary methodologies. The kinetics of this interconversion depends on the initial conversion (tuned by acidity and space time) and microporous topology, and involve: (i)â in the ZSM-5 catalysts, the diffusion of monocyclic aromatics toward the exterior of the zeolite to form coke, and (ii)â in the SAPO-18 catalysts, the obstruction of the cavities by aromatics that grow into tetracyclic aromatic islands.
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Among the structurally diverse collection of lipids that comprise the membrane lipidome, polyunsaturated phospholipids are particularly vulnerable to oxidation. The role of α-tocopherol (vitamin E) is to protect this influential class of membrane phospholipid from oxidative damage. Whether lipid-lipid interactions play a role in supporting this function is an unanswered question. Here, we compare the molecular organization of polyunsaturated 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylethanolamine (PDPE-d31) and, as a control, monounsaturated 1-[2H31]palmitoyl-2-oleoylphosphatidylethanolamine (POPE-d31) mixed with sphingomyelin (SM) and α-tocopherol (α-toc) (2:2:1 mol) by solid-state 2H NMR spectroscopy. In both cases the effect of α-toc appears similar. Spectral moments reveal that the main chain melting transition of POPE-d31 and PDPE-d31 is broadened beyond detection. A spectral component attributed to the formation of inverted hexagonal HII phase in coexistence with lamellar Lα phase by POPE-d31 (20 %) and PDPE-d31 (18 %) is resolved following the addition of α-toc. Order parameters in the remaining Lα phase are increased slightly more for POPE-d31 (7%) than PDPE-d31 (4%). Preferential interaction with polyunsaturated phospholipid is not apparent in these results. The propensity for α-toc to form phase structure with negative curvature that is more tightly packed at the membrane surface, nevertheless, may restrict the contact of free radicals with lipid chains on phosphatidylethanolamine molecules that accumulate polyunsaturated fatty acids.
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Bicamadas Lipídicas/química , Fosfatidiletanolaminas/química , Esfingomielinas/química , Vitamina E/química , Deutério , Espectroscopia de Ressonância Magnética , Estrutura MolecularRESUMO
Vitamin E (α-tocopherol) and a range of other biological compounds have long been known to promote the HII (inverted hexagonal) phase in lipids. Now, it has been well established that purely hydrophobic lipids such as dodecane promote the HII phase by relieving extensive packing stress. They do so by residing deep within the hydrocarbon core. However, we argue from X-ray diffraction data obtained with 1-palmitoyl-2-oleoylphosphatidylcholine (POPE) and 1,2-dioleoylphosphatidylcholine (DOPE) that α-tocopherol promotes the HII phase by a different mechanism. The OH group on the chromanol moiety of α-tocopherol anchors it near the aqueous interface. This restriction combined with the relatively short length of α-tocopherol (as compared to DOPE and POPE) means that α-tocopherol promotes the HII phase by relieving compressive packing stress. This observation offers new insight into the nature of packing stress and lipid biophysics. With the deeper understanding of packing stress offered by our results, we also explore the role that molecular structure plays in the primary function of vitamin E, which is to prevent the oxidation of polyunsaturated membrane lipids.
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Docosahexaenoic acid (DHA, 22:6) is an n-3 polyunsaturated fatty acid (n-3 PUFA) that influences immunological, metabolic, and neurological responses through complex mechanisms. One structural mechanism by which DHA exerts its biological effects is through its ability to modify the physical organization of plasma membrane signaling assemblies known as sphingomyelin/cholesterol (SM/chol)-enriched lipid rafts. Here we studied how DHA acyl chains esterified in the sn-2 position of phosphatidylcholine (PC) regulate the formation of raft and non-raft domains in mixtures with SM and chol on differing size scales. Coarse grained molecular dynamics simulations showed that 1-palmitoyl-2-docosahexaenoylphosphatylcholine (PDPC) enhances segregation into domains more than the monounsaturated control, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC). Solid state 2H NMR and neutron scattering experiments provided direct experimental evidence that substituting PDPC for POPC increases the size of raft-like domains on the nanoscale. Confocal imaging of giant unilamellar vesicles with a non-raft fluorescent probe revealed that POPC had no influence on phase separation in the presence of SM/chol whereas PDPC drove strong domain segregation. Finally, monolayer compression studies suggest that PDPC increases lipid-lipid immiscibility in the presence of SM/chol compared to POPC. Collectively, the data across model systems provide compelling support for the emerging model that DHA acyl chains of PC lipids tune the size of lipid rafts, which has potential implications for signaling networks that rely on the compartmentalization of proteins within and outside of rafts.
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Ácidos Docosa-Hexaenoicos/fisiologia , Microdomínios da Membrana/química , Varredura Diferencial de Calorimetria/métodos , Colesterol/química , Ácidos Docosa-Hexaenoicos/química , Bicamadas Lipídicas/química , Espectroscopia de Ressonância Magnética , Microdomínios da Membrana/fisiologia , Simulação de Dinâmica Molecular , Fosfatidilcolinas/química , Fosfatidilcolinas/fisiologia , Fosfatidiletanolaminas/química , Esfingomielinas/químicaRESUMO
Eicosapentaenoic (EPA, 20:5), docosahexaenoic (DHA, 22:6) and docosapentaenoic (DPA, 22:5) acids are omega-3 polyunsaturated fatty acids (n-3 PUFA) obtained from dietary consumption of fish oils that potentially alleviate the symptoms of a range of chronic diseases. We focus here on the plasma membrane as a site of action and investigate how they affect molecular organization when taken up into a phospholipid. All atom MD simulations were performed to compare 1-stearoyl-2-eicosapentaenoylphosphatylcholine (EPA-PC, 18:0-20:5PC), 1-stearoyl-2-docosahexaenoylphosphatylcholine (DHA-PC, 18:0-22:6PC), 1-stearoyl-2-docosapentaenoylphosphatylcholine (DPA-PC, 18:0-22:5PC) and, as a monounsaturated control, 1-stearoyl-2-oleoylphosphatidylcholine (OA-PC, 18:0-18:1PC) bilayers. They were run in the absence and presence of 20mol% cholesterol. Multiple double bonds confer high disorder on all three n-3 PUFA. The different number of double bonds and chain length for each n-3 PUFA moderates the reduction in membrane order exerted (compared to OA-PC, S¯CD=0.152). EPA-PC (S¯CD=0.131) is most disordered, while DPA-PC (S¯CD=0.140) is least disordered. DHA-PC (S¯CD=0.139) is, within uncertainty, the same as DPA-PC. Following the addition of cholesterol, order in EPA-PC (S¯CD=0.169), DHA-PC (S¯CD=0.178) and DPA-PC (S¯CD=0.182) is increased less than in OA-PC (S¯CD=0.214). The high disorder of n-3 PUFA is responsible, preventing the n-3 PUFA-containing phospholipids from packing as close to the rigid sterol as the monounsaturated control. Our findings establish that EPA, DHA and DPA are not equivalent in their interactions within membranes, which possibly contributes to differences in clinical efficacy.
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Membrana Celular/metabolismo , Ácidos Docosa-Hexaenoicos/farmacocinética , Ácido Eicosapentaenoico/farmacocinética , Ácidos Graxos Ômega-3/química , Ácidos Graxos Ômega-3/farmacocinética , Ácidos Graxos Insaturados/farmacocinética , Membrana Celular/química , Colesterol/metabolismo , Ácidos Docosa-Hexaenoicos/química , Ácido Eicosapentaenoico/química , Ácidos Graxos Ômega-3/classificação , Ácidos Graxos Ômega-3/metabolismo , Ácidos Graxos Insaturados/química , Fluidez de Membrana , Modelos Moleculares , Conformação Molecular , Simulação de Dinâmica MolecularRESUMO
The Accreditation Council for Graduate Medical Education requires medical training programs to monitor, track, and formally document a fellow's performance. If deficiencies are found, programs are expected to prepare and implement an effective plan of action for improvement and to ensure that graduates acquire the personal and professional attributes of an independent physician. We revised our evaluation policy and instituted a remediation protocol in 2008. Since that time, 130 pediatric anesthesia fellows have graduated. Seven fellows (5%) underwent departmental formal consultation for deficient behavior or poor performance. Of these 7 fellows, 4 underwent an individualized remediation program (IRP). A formal performance review and written contract, with specifically identified problems and general themes, recommendations for time-based successful behaviors, and clearly identified consequences for unsuccessful behaviors, was initiated for each fellow undergoing an IRP. All fellows who participated in this program completed their subspecialty training in pediatric anesthesia, and all eligible fellows have successfully achieved their subspecialty board certification. Our approach has the advantage of multimodality, time-based daily evaluations, and group discussions in the context of a Clinical Competency Committee. Utilization of an IRP as a metric for progress has features similar to effective cognitive behavioral therapy contracts and has ensured that our graduates are held to clearly delineated and specified skills and behaviors that allow them to work independently in the field of pediatric anesthesiology.
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Anestesiologia/educação , Competência Clínica/normas , Educação de Pós-Graduação em Medicina/métodos , Bolsas de Estudo , Pediatria/educação , Acreditação , HumanosRESUMO
BACKGROUND: Pediatric anesthesia-related cardiac arrest (ARCA) is an uncommon but potentially preventable adverse event. Infants and children with more severe underlying disease are at highest risk. We aimed to identify system- and anesthesiologist-related risk factors for ARCA. METHODS: We analyzed a prospectively collected patient cohort data set of anesthetics administered from 2000 to 2011 to children at a large tertiary pediatric hospital. Pre-procedure systemic disease level was characterized by ASA physical status (ASA-PS). Two reviewers independently reviewed cardiac arrests and categorized their anesthesia relatedness. Factors associated with ARCA in the univariate analyses were identified for reevaluation after adjustment for patient age and ASA-PS. RESULTS: Cardiac arrest occurred in 142 of 276,209 anesthetics (incidence 5.1/10,000 anesthetics); 72 (2.6/10,000 anesthetics) were classified as anesthesia-related. In the univariate analyses, risk of ARCA was much higher in cardiac patients and for anesthesiologists with lower annual caseload and/or fewer annual days delivering anesthetics (all P < 0.001). Anesthesiologists with the highest academic rank and years of experience also had higher odds of ARCA (P = 0.02). After risk adjustment for ASA-PS ≥ III and age ≤ 6 months, however, the association with lower annual days delivering anesthetics remained (P = 0.03), but the other factors were no longer significant. CONCLUSIONS: Case-mix explained most associations between higher risk of pediatric ARCA and anesthesiologist-related variables at our institution, but the association with fewer annual days delivering anesthetics remained. Our findings highlight the need for rigorous adjustment for patient risk factors in anesthesia patient safety studies.
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Anestesia/efeitos adversos , Parada Cardíaca/induzido quimicamente , Parada Cardíaca/epidemiologia , Adolescente , Fatores Etários , Anestesiologia/educação , Criança , Pré-Escolar , Estudos de Coortes , Mortalidade Hospitalar , Humanos , Incidência , Lactente , Recém-Nascido , Segurança do Paciente , Pediatria , Estudos Prospectivos , Risco Ajustado , Fatores de RiscoRESUMO
The direct acid-base reaction between ZnO/CoO/Co(OH)(2) and imidazolic ligands under moderate heating (100-160 °C), in a closed vessel, leads to the generation of the corresponding zinc/cobalt-imidazolates in a high yield (87-97%) in which network topology is controlled by the addition of small amounts of structure directing agents. Moreover, the fine tuning of the thermal process at the synthetic stage permits us to increase the crystal size, and even to grow X-ray quality single crystals.
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A series of isostructural copper(II) coordination polymers containing the nucleobase adenine and different monocarboxylic acids as bridging ligands, [Cu(2)(µ(3)-ade)(2)(µ(2)-OOC(CH(2))(n)CH(3))(2)]·xH(2)O (n from 0 to 5), have been prepared. Single-crystal X-ray analysis of acetate (n = 0) and butanoate (n = 2) compounds shows a covalent three-dimensional network in which the copper(II) centers are bridged by µ-N3,N7,N9-adeninato and µ-O,O'-carboxylato ligands, with crystallization water molecules trapped in the pores, which are decorated by the Watson-Crick faces of the adenine. The tunable permanent porosity of guest-free compounds was confirmed by gas adsorption measurements.
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Adenina/química , Ácidos Carboxílicos/química , Cobre/química , Técnicas Analíticas Microfluídicas , Compostos Organometálicos/química , Adsorção , Ligantes , Modelos Moleculares , Compostos Organometálicos/síntese química , Propriedades de SuperfícieRESUMO
The objective of this study was to detect interactions between relevant single-nucleotide polymorphisms (SNPs) associated with rheumatoid arthritis (RA). Data from Problem 1 of the Genetic Analysis Workshop 16 were used. These data consisted of 868 cases and 1,194 controls genotyped with the 500 k Illumina chip. First, machine learning methods were applied for preselecting SNPs. One hundred SNPs outside the HLA region and 1,500 SNPs in the HLA region were preselected using information-gain theory. The software weka was used to reduce colinearity and redundancy in the HLA region, resulting in a subset of 6 SNPs out of 1,500. In a second step, a parametric approach to account for interactions between SNPs in the HLA region, as well as HLA-nonHLA interactions was conducted using a Bayesian threshold least absolute shrinkage and selection operator (LASSO) model incorporating 2,560 covariates. This approach detected some main and interaction effects for SNPs in genes that have previously been associated with RA (e.g., rs2395175, rs660895, rs10484560, and rs2476601). Further, some other SNPs detected in this study may be considered in candidate gene studies.
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Objectives of the International Society for Hepatic Encephalopathy and Nitrogen Metabolism Commission were to identify well-characterized animal models of hepatic encephalopathy (HE) and to highlight areas of animal modelling of the disorder that are in need of development. Features essential to HE modelling were identified. The best-characterized animal models of HE in acute liver failure, the so-called Type A HE, were found to be the hepatic devascularized rat and the rat with thioacetamide-induced toxic liver injury. In case of chronic liver failure, surgical models in the rat involving end-to-side portacaval anastomosis or bile duct ligation were considered to best model minimal/mild (Type B) HE. Unfortunately, at this time, there are no satisfactory animal models of Type C HE resulting from end-stage alcoholic liver disease or viral hepatitis, the most common aetiologies encountered in patients. The commission highlighted the urgent need for such models and of improved models of HE in chronic liver failure in general as well as a need for models of post-transplant neuropsychiatric disorders. Studies of HE pathophysiology at the cellular and molecular level continue to benefit from in vitro and or ex vivo models involving brain slices or exposure of cultured cells (principally cultured astrocytes) to toxins such as ammonia, manganese and pro-inflammatory cytokines. More attention could be paid in the future to in vitro models involving the neurovascular unit, microglia and neuronal co-cultures in relation to HE pathogenesis.
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Modelos Animais de Doenças , Encefalopatia Hepática/classificação , Encefalopatia Hepática/patologia , Animais , Ratos , Sociedades CientíficasRESUMO
OBJECTIVES: The grading of hepatic encephalopathy (HE) is based on a combination of indicators that reflect the state of consciousness, intellectual function, changes in behavior, and neuromuscular alterations seen in patients with liver failure. METHODS: We modified the traditional West Haven criteria (WHC) to provide an objective assessment of the cognitive parameters to complement the subjective clinical ratings for the performance of extracorporeal albumin dialysis (ECAD) using a molecular adsorption recirculating system in patients with cirrhosis and severe (grade III / IV) encephalopathy. The HE Scoring Algorithm (HESA) combined clinical indicators with those derived from simple neuropsychological tests,the latter more often used in milder grades of HE (I / II). The performance of each indicator was compared across grades and sites. RESULTS: Results of HESA were also compared with the Glasgow Coma Scale. A total of 597 evaluations were performed in patients randomized to ECAD plus standard medical therapy or the latter only. Most parameters exhibited significant separation between grades; the most effective indicators were lack of verbal, eye, and motor response (grade IV), somnolence and disorientation to place (grade III), and lethargy and disorientation to time (grade II). Two clinical and four neuropsychological indicators were useful to classify patients as grade I. The Glasgow Coma Scale differed among the four stages of the WHC, but the differences between grades I and II were small and not clinically useful. CONCLUSION: HESA extends the traditional WHC for grading HE. In the absence of a "gold" standard, the most useful indicators noted in this trial should be further validated.