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Duchenne muscular dystrophy (DMD) is a lethal muscle disease caused by absence of the protein dystrophin, which acts as a structural link between the basal lamina and contractile machinery to stabilize muscle membranes in response to mechanical stress. In DMD, mechanical stress leads to exaggerated membrane injury and fiber breakdown, with fast fibers being the most susceptible to damage. A major contributor to this injury is muscle contraction, controlled by the motor protein myosin. However, how muscle contraction and fast muscle fiber damage contribute to the pathophysiology of DMD has not been well characterized. We explored the role of fast skeletal muscle contraction in DMD with a potentially novel, selective, orally active inhibitor of fast skeletal muscle myosin, EDG-5506. Surprisingly, even modest decreases of contraction (

Abstract Background During the COVID-19 pandemic, multiple countries have taken measures, such as isolation and quarantine, to prevent person-to-person spread of disease. These actions forced many physicians to adopt new techniques, such as telemedicine, to continue patient care, which has proven to be useful in continued care for those with non-COVID-19 pathologies. Various factors, such as security, confidentiality, cost-effectiveness, comfort, and the risk of malpractice, influence the perception of telemedicine among medical practitioners. The aim of this study was to adapt an existing instrument and validate it into a new Spanish version. The instrument is about the perceptions and knowledge of telemedicine in healthcare professionals. Methods The original questionnaire surveyed 6 domains with 40 questions, and each question was measured with a five-point Likert scale ranging from very high [5] to very low [1]. The survey was translated to Spanish using machine translation. The translation was reviewed independently, and then, a consensus was achieved regarding minor changes in the syntax of the survey to facilitate understanding. After expert feedback and questionnaire review, the research team members proposed reducing the instrument to 13 items in 4 domains due to the similarity of some questions. The sample was divided into 2randomly selected groups. Eligibility criteria included physicians providing private or public services with active medical/clinical practice. Results In total, 382 surveys were collected and separated into two random samples, S1 and S2 (198 and 184, respectively). In exploratory factor analysis (EFA), the 13 items were grouped into four theoretical domains, and item 7 presented cross loading between factors and was removed. Confirmatory factor analysis was performed to assess the scale reliability and interscale associations; three models were tested. Global Cronbach’s alpha for internal consistency was 0.76 for the EFA. The goodness of fit measures root mean square error of approximation and comparative fit index were 0.009 and 0.999, respectively, for the best model. Conclusions The translated instrument was clear, with adequate internal consistency, readability, and appropriate for application in the physician setting. This validated questionnaire made it possible to evaluate physicians’ knowledge of telemedicine to increase its use, especially during the COVID-19 pandemic.

The present paper seeks to address a gap in the literature regarding green marketing and examines the relationship between ecological concern, inward and outward environmental attitudes, purchasing behavior and environmental behavior as antecedents of green purchasing behavior. The data was gathered through an online survey carried out in Portugal with 530 valid answers. Structural Equation Modelling Partial Least Squares (SEM-PLS) was used to evaluate the model. A t-test was applied to identify differences between men and women. The results show that ecological concern, environmental attitude, environmental behavior and purchase intention are good predictors of green purchase behavior. Women scored higher than men on all variables, meaning that they are indeed superior environmentalists than men. Green purchase behavior is strongly influenced by both purchase intention and environmental behavior, so green brands should focus on targeting individuals that already take some actions in what concerns the environment, or to those who intend to do so.

On-site partial discharge (PD) measurements have turned out to be a very efficient technique for determining the insulation condition in high-voltage electrical grids (AIS, cable systems, GIS, HVDC converters, etc.); however, there is not any standardised procedure for determining the performances of PD measuring systems. In on-line and on-site PD measurements, high-frequency current transformers (HFCTs) are commonly used as sensors as they allow for monitoring over long distances in high-voltage installations. To ensure the required performances, a metrological qualification of the PD analysers by applying an evaluation procedure is necessary. A novel evaluation procedure was established to specify the quantities to be measured (electrical charge and PD repetition rate) and to describe the evaluation tests considering the measured influence parameters: noise, charge amplitude, pulse width and time interval between consecutive pulses. This procedure was applied to different types of PD analysers used for off-line measurements, sporadic on-line measurements and continuous PD monitoring. The procedure was validated in a round-robin test involving two metrological institutes (RISE from Sweden and FFII from Spain) and three universities (TUDelft from the Netherlands, TAU from Finland and UPM from Spain). With this round-robin test, the effectiveness of the proposed qualification procedure for discriminating between efficient and inappropriate PD analysers was demonstrated. Furthermore, it was shown that the PD charge quantity can be properly determined for on-line measurements and continuous monitoring by integrating the pulse signals acquired with HFCT sensors. In this case, these sensors must have a flat frequency spectrum in the range between several tens of kHz and at least two tens of MHz, where the frequency pulse content is more significant. The proposed qualification procedure can be useful for improving the future versions of the technical specification TS IEC 62478 and the standard IEC 60270.

The insulation condition of HVDC grids consisting of cable systems, GIS, and converters should be monitored by partial discharge (PD) analysers using artificial intelligence (AI) tools for efficient insulation diagnosis. Although there are many experiences of PD monitoring solutions developed for the supervision of the insulation condition of HVAC grids using PD analysers, there are no standardised requirements for their qualification available yet. The international technical specification TS IEC 62478 provides general rules for PD measurements using electromagnetic methods but does not define performance requirements for qualification tests. HVDC and HVAC PD analysers must be tested by unambiguous test procedures. This paper compiles experiences of using PD analysers with HFCT sensors in HVAC grids (cable systems, GIS, and AIS) to define a qualification procedure for HVAC systems. This procedure is applicable to HVDC grids (cable systems, GIS, AIS, and converters) because the particularities related to the insulation behaviour under HVDC voltage are also considered. Representative PD sources are discussed in HVAC and HVDC positive and negative polarity. The PD pulse trend of representative insulation defects in HVDC cable systems is quite different from that of HVAC grids. Special attention should be paid to the acquisition of PD signals in HVDC grids since few pulses appear in solid insulations, mainly during voltage changes (polarity reversals or surges), but rarely in continuous operation with constant direct voltage. A synthetic PD simulator has been developed to reproduce trains of PD pulses or noise signals, similar to those that can appear in the power network. A set of three functionality tests has been developed for qualification of the diagnostic capabilities of PD analysers working up to 30 MHz addressed to HVDC or HVAC grids: (1) PD recognition test, (2) PD clustering test, and (3) PD location test. This qualification procedure has been validated by means of a round-robin test performed by five research institutes (RISE, FFII, TUDelft, TAU, and UPM) using commercial and in-development AI PD recognition and clustering tools to demonstrate its robustness and applicability. Applying this qualification procedure, two PD methods for electrical detection and prevention of insulation defects have been approved, one for HVAC and the other for HVDC grids.

Strong earthquakes (magnitude ≥7) occur worldwide affecting different cities and countries while causing great human, ecological and economic losses. The ability to forecast strong earthquakes on the long-term basis is essential to minimize the risks and vulnerabilities of people living in highly active seismic areas. We have studied seismic activities in North America, South America, Japan, Southern China and Northern India in search for patterns in strong earthquakes on each of these active seismic zones between 1900 and 2021 with the powerful mathematical tool of wavelet transform. We found that the primary seismic activity patterns for M ≥ 7 earthquakes are 55, 3.7, 7.7, and 8.6 years, for seismic zones of the southwestern United States and northern Mexico, southwestern Mexico, South American, and Southern China-Northern India, respectively. In the case of Japan, the most important seismic pattern for earthquakes with magnitude 7 ≤ M< 8 is 4.1 years and for strong earthquakes with M ≥ 8, it is 40 years. Every seismic pattern obtained clusters the earthquakes in historical intervals/episodes with and without strong earthquakes in the individually analyzed seismic zones. We want to clarify that the intervals where no strong earthquakes do not imply the total absence of seismic activity because earthquakes can occur with lesser magnitude within this same interval. From the information and pattern we obtained from the wavelet analyses, we created a probabilistic, long-term earthquake prediction model for each seismic zone using the Bayesian Machine Learning method. We propose that the periods of occurrence of earthquakes in each seismic zone analyzed could be interpreted as the period in which the stress builds up on different planes of a fault, until this energy releases through the rupture along faults and fractures near the plate tectonic boundaries. Then a series of earthquakes can occur along the fault until the stress subsides and a new cycle begins. Our machine learning models predict a new period of strong earthquakes between 2040 ± 5 and 2057 ± 5, 2024 ± 1 and 2026 ± 1, 2026 ± 2 and 2031 ± 2, 2024 ± 2 and 2029 ± 2, and 2022 ± 1 and 2028 ± 2 for the five active seismic zones of United States, Mexico, South America, Japan, and Southern China and Northern India, respectively. In additon, our methodology can be applied in areas where moderate earthquakes occur, as for the case of the Parkfield section of the San Andreas fault (California, United States). Our methodology explains why a moderate earthquake could never occur in 1988 ± 5 as proposed and why the long-awaited Parkfield earthquake event occurred in 2004. Furthermore, our model predicts that possible seismic events may occur between 2019 and 2031, with a high probability of earthquake events at Parkfield around 2025 ± 2 years.

Abstract Background The use of information and communication technologies (ICTs) provide the tools for enabling fast and reliable real-time communications, as well as the transfer of information between dental professionals and their patients. However, little is known about the frequency and preference of ICTs among Latin-American dentists. Our study aims to fill this gap by assessing different aspects related to ICTs, mainly the frequency of use, perceptions, and barriers among Ecuadorian dentists. Methods An anonymous, cross-sectional survey-based study was conducted among 342 Ecuadorian dentists. The final questionnaire included 13 items related to the frequency of use, perceptions, and barriers of ICTs. Bivariate analysis was performed by using chi-squared testing to explore the association between the independent variables and the intended use of ICTs, as well as to characterize the perceptions and barriers related to ICTs. Results In general, most participants reported the use of ICTs to communicate with colleagues (99.7%), and patients (96.2%), while only 63.5% reported using ICTs to obtain academic information in their daily practice. WhatsApp was rated as the most used ICT for communicating with colleagues and patients. A majority of participants considered that ICTs can be useful for facilitating continuing dental education (92.1%), searching new work opportunities (91.5%), promoting health (90.1%), working with colleagues and other health professionals (91.2%), promoting their professional services (90.6%), and for resolving clinical cases (87.7%). On the subject of barriers, privacy and security concerns about personal and/or patient information was the biggest concern among dentists (65%), followed by lack of time to learn how to use and/or use ICTs (48%), lack of mobile internet access (28.1%), and lack of internet access at work (24.9%). Conclusion In our study, we found that Ecuadorian dentists had a high usage rate of ICTs, mainly for communicating with other colleagues and patients, while the academic use of technology remains a comparatively underused application. Most of the participants surveyed had a positive perception towards ICTs, while privacy and security concerns were identified as the main barrier. Older age was associated with a less favourable perception toward ICTs, as well as an increased likelihood of reporting barriers related to the use of technology.

Abstract Background Gathering ecological data for species of conservation concern inhabiting remote regions can be daunting and, sometimes, logistically infeasible. We built a custom-made GPS tracking device that allows to remotely and accurately collect animal position, environmental, and ecological data, including animal temperature and UVB radiation. We designed the device to track the critically endangered Galápagos pink land iguana, Conolophus marthae. Here we illustrate some technical solutions adopted to respond to challenges associated with such task and present some preliminary results from controlled trial experiments and field implementation. Results Our tests show that estimates of temperature and UVB radiation are affected by the design of our device, in particular by its casing. The introduced bias, though, is systematic and can be corrected using linear and quadratic regressions on collected values. Our data show that GPS accuracy loss, although introduced by vegetation and orientation of the devices when attached to the animals, is acceptable, leading to an average error gap of less than 15 m in more than 50% of the cases. Conclusions We address some technical challenges related to the design, construction, and operation of a custom-made GPS tracking device to collect data on animals in the wild. Systematic bias introduced by the technological implementation of the device exists. Understanding the nature of the bias is crucial to provide correction models. Although designed to track land iguanas, our device could be used in other circumstances and is particularly useful to track organisms inhabiting locations that are difficult to reach or for which classic telemetry approaches are unattainable.

El trabajo estudió la frecuencia de sensibilidad estacional en una muestra de población austral chilena, alta latitud sur y su relación con actividades laborales desarrolladas en diferentes turnos de trabajo y con variables de adaptación general. Un total de 465 personas participaron respondiendo instrumentos midiendo estacionalidad (SPAQ), felicidad subjetiva (Escala de Oxford), adaptación social (Bell) y ansiedad y depresión (MASQE30). Los resultados principales indican que la frecuencia de sensibilidad estacional es alta, su nivel declarado en promedio es moderado, en su límite superior, y es evaluada como de impacto negativo significativo en la vida diaria. Respecto de los patrones estacionales, el más numeroso fue el de verano, que indica que las personas perciben beneficios con el aumento de luz, lo que correlaciona negativamente con la felicidad. Los análisis según turno de trabajo mostraron perfiles diferenciales para cada uno. Se discuten estos resultados en torno a su importancia para el desarrollo de políticas públicas asociadas a la salud física y mental de poblaciones australes.

El gobierno de Colombia y el grupo guerrillero FARC-EP han firmado en la Habana Cuba el 24 de noviembre de 2016, acuerdos que permitirán impulsar el desarrollo local, así como, crear capacidades que aceleren el desarrollo y le devuelva a la población del Catatumbo la tranquilidad física y emocional. El objetivo principal consiste en identificar la gestión de la cooperación internacional en el acuerdo de paz para la región del Catatumbo, generando para ello un proceso de formación encaminado al reforzamiento del tejido institucional, organizacional e individual para promocionar el desarrollo local de las zonas de alta migración de grupos insurgentes. El proceso metodológico de la investigación y del constructo teórico, se desarrolló dentro del paradigma post-positivista, con un enfoque epistemológico cualitativo. Entre los resultados destacan: En la zona del Catatumbo aún se perciben problemas de seguridad y la participación de otros grupos que no están en el acuerdo de paz; asimismo, se evidenció la existencia de los elementos que conforman la gestión de la cooperación internacional en la zona. Se concluye que, hace falta generar políticas, mecanismos o canales de difusión del acuerdo de paz en pro del beneficio de la población vinculada a la región del Catatumbo.

The enzymatic synthesis of short-tailed alkyl glucosides is generally carried out in an aqueous-organic biphasic reaction medium with a rather low fatty alcohol concentration in the aqueous phase (where the synthesis occurs). Thus, hydrolytic reactions have a significant impact on the synthesis performance. Given this background, the use of acetone as cosolvent was studied for the synthesis of butyl-β-galactoside with Aspergillus oryzae β-galactosidase. The liquid–liquid equilibrium of the reaction mixture components (acetone/1-butanol/aqueous solution) was determined and the single- and two-phase regions were defined at 30, 40, and 50°C. It was observed that the liquid–liquid equilibrium of the ternary system acetone/1-butanol/water differs significantly from the one obtained using an aqueous solution (50 mM McIlvaine buffer pH 4.5; 5 g L–1) instead of water. This is mainly because of the salting-out effect of the buffer; nevertheless, the presence of lactose also altered the equilibrium. Having this in mind, the effects of temperature (30 and 50°C) and reaction mixture composition were assessed. Three general conditions were evaluated: single-phase ternary system (30% acetone), two-phase ternary system (10% acetone) and two-phase binary system (0% acetone). Acetone had a deleterious effect on enzyme stability at 50°C, leading to low reaction yields. However, no enzyme deactivation was detected at 30°C. Moreover, a reaction yield of 0.98 mol mol–1 was attained in the 30/50/20% (w/w) mixture of acetone/1-butanol/aqueous solution. This very high yield can be explained by the huge increase in the concentration of 1-butanol and the reduction of water activity. The synthesis was carried out using also the β-galactosidase immobilized in glyoxal-agarose and amino-glyoxal-agarose, and by aggregation and crosslinking. In the case of agarose-derived catalysts, two average particle diameters were assessed to evaluate the presence of internal mass transfer limitations. Best yield (0.88 mol mol–1) was obtained with glyoxal-agarose derivatives and the particle size had non-effect on yield. The chemical structure of butyl-β-galactoside was determined by NMR and FT-IR.

Lactulose synthesis from fructose and lactose in continuous stirred tank (CSTR) reactor operation with glyoxyl-agarose immobilized Aspergillus oryzae β-galactosidase is reported for the first time. The effect of operational variables: inlet concentrations of sugar substrates, temperature, feed substrate molar ratio, enzyme loading and feed flow rate was studied on reactor performance. Even though the variation of each one affected to a certain extent lactulose yield (YLactulose), specific productivity (πLactulose) and selectivity of the reaction (lactulose/transgalactosylated oligosaccharides molar ratio) (SLu/TOS), the most significant effects were obtained by varying the inlet concentrations of sugar substrates and the feed substrate molar ratio. Maximum YLactulose of 0.54 g⋅g–1 was obtained at 50°C, pH 4.5, 50% w/w inlet concentrations of sugar substrates, feed flowrate of 12 mL⋅min–1, fructose/lactose molar ratio of 8 and reactor enzyme load of 29.06 IUH⋅mL–1. At such conditions SLu/TOS was 3.7, lactose conversion (XLactose) was 0.39 and total transgalactosylation yield was 0.762 g⋅g–1, meaning that 76% of the reacted lactose corresponded to transgalactosylation and 24% to hydrolysis, which is a definite advantage of this mode of operation. Even though XLactose in CSTR was lower than in other reported modes of operation for lactulose synthesis, transgalactosylation was more favored over hydrolysis which reduced the inhibitory effect of galactose on β-galactosidase.

El desarrollo de la administración tributaria a nivel internacional deriva en instrumentos novedosos de política fiscal que apuntan al incremento de la dinámica territorial Esta tendencia se aprecia también en los países de América Latina. Un caso particular se trata en la presente investigación, donde se reflejan los resultados de un estudio comparativo entre la estructura fiscal y la administración tributaria vigentes en el año 2014 en los Municipios de Manta, (Ecuador) y Holguín, (Cuba); a partir de un sistema de indica- dores generalmente aceptado para tales fines. Este trabajo tiene valor metodológico y formativo, pues el material obtenido puede ser utilizado por los docentes de la carrera de Economía y los especialistas encargados de la administración tributaria, tanto en Manta como en Holguín para fines de capacitación y selección de alternativas. Palabras clave: Estructura fiscal, administración tributaria, método comparativo.

Las universidades han sido consideradas como instituciones generadoras y difusoras de nuevos conocimientos científicos y tecnológicos, siendo la investigación la fuente principal de estos conocimientos, los cuales deben ser gestionados para su creación, difusión y transferencia que explican la necesidad de abordar la gestión del conocimiento como mecanismo de acción para el diseño de estrategias de desarrollo basadas en la utilización del conocimiento en la universidad, como recurso estratégico y significativo orientado al desarrollo sustentable.

Low-cost tungsten monometallic catalysts containing variable amounts of metal (4.5, 7.1 and 8.5%W) were prepared by impregnating alumina with ammonium metatungstate as an inexpensive precursor. The catalysts were characterized using ICP, XPS, XRD, TPR and hydrogen chemisorption. These techniques revealed mainly WO3-Al2O3 (W6+) species on the surface. The effects of the content of W nanoparticles and reaction temperature on activity and selectivity for the partial hydrogenation of 3-hexyne, a non-terminal alkyne, were assessed under moderate conditions of temperature and pressure. The monometallic catalysts prepared were found to be active and stereoselective for the production of (Z )-3-hexene, had the following order: 7.1WN/A > 8.5 WN/A ≥ 4.5 WN/A. Additionally, the performance of the synthesized xWN/A catalysts exhibited high sensitivity to temperature variation. In all cases, the maximum 3-hexyne total conversion and selectivity was achieved at 323 K. The performance of the catalysts was considered to be a consequence of two phenomena: a) the electronic effects, related to the high charge of W (+6), causing an intensive dipole moment in the hydrogen molecule (van der Waals forces) and leading to heterolytic bond rupture; the H+ and H- species generated approach a 3-hexyne adsorbate molecule and cause heterolytic rupture of the C≡C bond into C- = C+; and b) steric effects related to the high concentration of WO3 on 8.5WN/A that block the Al2O3 support. Catalyst deactivation was detected, starting at about 50 min of reaction time. Electrodeficient W6+ species are responsible for the formation of green oil at the surface level, blocking pores and active sites of the catalyst, particularly at low reaction temperatures (293 and 303 K). The resulting best catalyst, 7.1WN/A, has low fabrication cost and high selectivity for (Z )-3-hexene (94%) at 323 K. This selectivity is comparable to that of the classical and more expensive industrial Lindlar catalyst (5 wt% Pd). The alumina supported tungsten catalysts are low-cost potential replacements for the Lindlar industrial catalyst. These catalysts could also be used for preparing bimetallic W-Pd catalysts for selective hydrogenation of terminal and non-terminal alkynes.

El presente artículo tiene como propósito identificar las competencias necesarias para el ejercicio efectivo del docente universitario, específicamente las competencias clave y cardinales, para que finalmente se integren en un perfil de competencias profesionales que contribuyan a mejorar su desempeño. Este proceso permitiría además de valorar el trabajo docente, identificaría las habilidades, destrezas, talentos y experiencias entre otros, que debe presentar un docente para responder a la dinámica universitaria actual; asumiendo la universidad con esto, la gestión del talento humano por competencias, permitiendo demostrar estos comportamientos de alto nivel, que garanticen el éxito de sus actividades académicas.

Anti-Xa test measures the activity of heparin against the activity of activated coagulation factor X; significant variability of anti-Xa levels in common clinical scenarios has been observed. Objective. To review the most common clinical settings in which anti-Xa results can be bias. Evidence Review. Guidelines and current literature search: we used PubMed, Medline, Embase, and MEDION, from 2000 to October 2013. Results. Anti-Xa test is widely used; however the assay underestimates heparin concentration in the presence of significant AT deficiency, pregnancy, end stage renal disease, and postthrombolysis and in patients with hyperbilirubinemia; limited published data evaluating the safety and effectiveness of anti-Xa assays for managing UH therapy is available. Conclusions and Relevance. To our knowledge this is the first paper that summarizes the most common causes in which this assay can be affected, several “day to day” clinical scenarios can modify the outcomes, and we concur that these rarely recognized scenarios can be affected by negative outcomes in the daily practice.

Hyptis suaveolens is a medicinal plant that is, according to traditional medicine, considered useful in the treatment of gastric ulcers. Although its gastroprotective activity was reported, the active compounds have not been identified. Therefore, the aim of the present study was to identify at least one active compound potentially responsible for the gastroprotective activity of H. suaveolens by using a bioassay guided study with an ethanol-induced gastric ulcer experimental model in rats. The results show that the hexane extract had protective activity (close to 70% when using doses between 10 and 100 mg/kg), and that the compound suaveolol, isolated from this extract, was one of the active gastroprotective agents. This is the first report about the gastroprotective activity of suaveolol. Rats treated with this compound at 3, 10, 30 and 100 mg/kg showed 12.6, 21.3, 39.6 and 70.2% gastroprotection respectively. The effect elicited by suaveolol (at 100 mg/kg) was attenuated by pretreatment with either NG-nitro-L-arginine methyl ester (70 mg/kg, i.p.), a nitric oxide (NO) synthase inhibitor, indomethacin (10 mg/kg, s.c.), a blocker of prostaglandin synthesis, or N-ethylmaleimide (10 mg/kg, s.c.), a blocker of sulfhydryl groups. This suggests that the gastroprotective mechanism of action of this compound involves NO, prostaglandins and sulfhydryl groups.

Two complexes of Rh(I) and Pd(II) with chloride and tridecylamine ligands were obtained and characterized by Elementary Analysis and by XPS and FTIR spectroscopies. Complexes anchored on γ-Al2O3 were tested in the styrene semi-hydrogenation reaction carried out in the absence or presence of a sulfur poison. Although both low loaded catalysts were highly selective, the Pd(II) complex was three times more active than the Rh(I) complex. The rhodium complex was more sulfur resistant but less active than the palladium complex. Differences in conversion and sulfur resistance between both complexes could be related to electronic and/or geometric effects.

Se presenta un modelo de sistema dinámico híbrido utilizando la lógica difusa. Para lograr esto se hace una breve descripción de los principales enfoques que se tienen en la actualidad de los sistemas dinámicos híbridos desarrollando las ecuaciones básicas de los bloques que conforman el modelo. Actualmente la teoría del control se ha centrado en el estudio por separado de la dinámica continua y la dinámica discreta; sin embargo, es necesario introducir el estudio de la combinación de ambos en un solo tratado. En el ámbito industrial los procesos son dinámicos y toda su estructura de control está basada en la teoría de la lógica digital. Sin embargo existe el paradigma de la lógica difusa, la cual se introduce en este artículo para proponer un nuevo enfoque. Cabe mencionar que para validar el modelo se utilizan herramientas computacionales de simulación de sistemas dinámicos.

Objetivo: Determinar la integridad funcional de la vía auditiva en el tronco encefálico a través de las respuestas evocadas auditivas del tronco encefálico (ABR) en niños con retardo en el lenguaje sin patología en oído medio y sistema nervioso central y sin factores de riesgo de hipoacusia neonatal. Diseño: Estudio retrospectivo transversal. Lugar: Servicios de otorrinolaringología del Centro Médico Naval y del Hospital Central de la Fuerza Aérea del Perú. Material y Métodos: Se analizó el ABR realizado en los últimos diez años a niños con retardo en el lenguaje, que incluyó 48 niños, 28 varones y 20 mujeres, con edades entre 1 y 11 años. Se evaluó los tiempos de latencia y la morfología de las ondas I, II, III, IV y V del ABR. Resultados: Se encontró las latencias dentro de lo normal para cada edad. En 77% de los pacientes hubo distorsión morfológica y/o hipovoltaje de las ondas, más frecuentemente (58%) en las ondas I y II, correspondientes al nervio auditivo y núcleos cocleares en el tronco encefálico. Conclusiones: Los resultados sugieren que existe trastorno en la sincronización neural de la vía auditiva en el VIII par y en el tronco encefálico en 77% de los pacientes evaluados, lo cual afectaría el procesamiento auditivo central.

The glycerol hydrogenolysis reaction was performed in a continuous flow trickle bed reactor using a water glycerol feed and both copper chromite and Cu/Al2O3 catalysts. The commercial copper chromite had a higher activity than the laboratory prepared Cu/Al2O3 and was used for most of the tests. Propylene glycol was the main product with both catalysts, acetol being the main by-product. It was found that temperature is the main variable influencing the conversion of glycerol. When the state of the glycerol-water reactant mixture was completely liquid, at temperatures lower than 190 ºC, conversion was low and deactivation was observed. At reaction temperatures of 210-230 ºC the conversion of glycerol was complete and the selectivity to propylene glycol was stable at about 60-80% all throughout the reaction time span of 10 h, regardless of the hydrogen pressure level (1 to 20 atm). These optimal values could not be improved significantly by using other different reaction conditions or increasing the catalyst acidity. At higher temperatures (245-250 ºC) the conversion was also 100%. Under reaction conditions at which copper chromite suffered deactivation, light by-products and surface deposits were formed. The deposits could be completely burned at 250 ºC and the catalyst activity fully recovered.

The influence of the kind of metal precursor and the sequence of impregnation on the properties of Pd-Ni catalysts was evaluated during the test reaction of selective hydrogenation of styrene to ethylbenzene by means of physicochemical characterization. The focus was put on the final hydrogenating activity and the resistance to deactivation by sulfided compounds (thiophene). The used techniques of characterization were ICP, XPS, XDR, TPR, CO chemisorption and TEM. XPS results indicated the presence of different Pd species: Pdδ-, Pdº and Pdδ+. In the case of the Ni containing catalysts, Niº and NiO species were also detected. These palladium and nickel species would be responsables of the variation of activity and sulfurresistance of the catalysts. NiClPd catalysts had a higher resistance to deactivation by sulfur poisoning. This was associated to a higher concentration of Pdη+ClxOy species that would prevent the adsorption of thiophene by both steric and electronic effects. It could also be due to the lower concentration of Pdº and Niº on these catalysts, as compared to those shown by the PdNiCl catalysts. Both the Pdº and Niº species are more prone to poisoning because of their higher electronic availability.