Mezclas de microfibras de poliláctida y polietilenglicol: material compuesto con aplicaciones biomédicas

En este proyecto se ha realizado el estudio de un nuevo material compuesto conformado como una matriz de microfibras de dos biopolímeros de diferentes hidrofobicidades, polilactida (PLA, hidrofóbico) y polietilenglicol (PEG, hidrofílico). Las fibras se obtuvieron mediante la técnica de electrospinning o electrohilado de dos disoluciones independientes de cada homopolímero. Para ello, los dos sistemas de inyección fueron posicionados a 180º el uno del otro (en direcciones opuestas), y las electrofibras producidas recogidas en un colector giratorio colocado a una distancia media entre ambas agujas, lo cual permite una superposición de las fibras producidas para obtener matrices con distribución homogénea de ambos polímeros. Matrices con diferentes composiciones de PLA/PEG fueron obtenidas fijando el flujo de la disolución de PEG y variando el flujo de la disolución de PLA. Las matrices de fibras fueron caracterizadas morfológicamente por microscopia electrónica de barrido (SEM); sus propiedades térmicas se determinaron por calorimetría diferencial de barrido (DSC) y por termogravimetría (TGA).También se estudió la estabilidad de las matrices después de eliminar las fibras de PEG mediante su disolución en agua. Así, fueron determinadas las modificaciones estructurales (morfología y diámetro de fibras) mediante SEM, y la pérdida de PEG fue cuantificada por resonancia magnética nuclear (RMN), y cualitativamente demostrada por FTIR. Las matrices fueron funcionalizadas para una actividad antibacteriana. Para ello, se prepararon matrices cargando en las fibras de PLA el antimicrobiano Triclosan 1 % (TCS) o el polímero antimicrobiano Polihexametilenbiguanida 0,25 % (PHMB). En estas matrices se estudió el comportamiento de liberación de los antimicrobianos en dos medios: en medio con carácter hidrofílico, tampón fosfato salino (PBS), y en medio con carácter hidrofóbico, PBS suplementado al 70 % con etanol absoluto (PBS-EtOH 70 %).Finalmente, se determinó la actividad antimicrobiana de las matrices mediante ensayos microbiológicos de inhibición del crecimiento y adhesión bacteriana. Asimismo, se determinó su biocompatibilidad y aplicación como plataforma 3D para la adhesión y la proliferación celular mediante ensayos de cultivo in-vitro de líneas celulares

Analysis of reactive power strategies in HVDC-connected wind power plant clusters

© 2017 John Wiley & Sons, Ltd. Offshore wind power plants (WPPs) built near each other but far from shore usually connect to the main grid by a common high-voltage DC (HVDC) transmission system. In the resulting decoupled offshore grid, the wind turbine converters and the high-voltage DC voltage-source converter share the ability to inject or absorb reactive power. The overall reactive power control dispatch influences the power flows in the grid and hence the associated power losses. This paper evaluates the respective power losses in HVDC-connected WPP clusters when applying 5 different reactive power control strategies. The case study is made for a 1.2-GW-rated cluster comprising 3 WPP and is implemented in a combined load flow and converter loss model. A large set of feasible operating points for the system is analyzed for each strategy. The results show that a selection of simulations with equal wind speeds is sufficient for the annual energy production comparison. It is found that the continuous operation of the WPPs with unity power factor has a superior performance with low communication requirements compared with the other conventional strategies. The optimization-based strategy, which is developed in this article, allows a further reduction of losses mainly because of the higher offshore grid voltage level imposed by the high-voltage DC voltage-source converter. Reactive power control in HVDC-connected WPP clusters change significantly the overall power losses of the system, which depend rather on the total sum of the injected active power than on the variance of wind speeds inside the cluster.Postprint (author's final draft

Handling of unbalanced faults in HVDC-connected wind power plants

High-voltage DC (HVDC) connections enable integration of wind power plants located very far from shore. The decoupled AC offshore grid comprises multiple WT converters, and the voltage magnitude and frequency is primarily controlled by the offshore high-voltage DC voltage-source converter (VSC-HVDC). Faults in the offshore grid challenge the connected converters to provide an adequate response improving the overall fault behavior. Of special interest are asymmetrical faults due to the resulting unbalanced voltage conditions. This article addresses such conditions in the offshore grid and analyzes the impact on the offshore grid behavior for different converter contributions. Four fault ride-through strategies are studied for the WT converters. The effect of over-modulation of the converter voltages during such voltage conditions is highlighted. A test system is defined to analyze the fault and post-fault behavior. It is found that voltage support from the WT converters in both positive and negative sequence shows the best performance compared to controlled negative sequence current suppression. This scheme helps additionally the VSC-HVDC AC voltage control to return quickly to normal operation. To validate this statement simulations are performed for line-to-line (LL) and single line-to-ground (SLG) faults in immediate vicinity of the VSC-HVDC.Peer ReviewedPostprint (author's final draft

Optimization-based reactive power control in HVDC-connected wind power plants

One application of high–voltage dc (HVdc) systems is the connection of remotely located offshore wind power plants (WPPs). In these systems, the offshore WPP grid and the synchronous main grid operate in decoupled mode, and the onshore HVdc converter fulfills the grid code requirements of the main grid. Thus, the offshore grid can be operated independently during normal conditions by the offshore HVdc converter and the connected wind turbines. In general, it is well known that optimized reactive power allocation might lower the component loading and power losses. This paper aims to propose and assess a reactive power allocation optimization within HVdc–connected WPPs. For these systems, the offshore converter operates the adjoining grid by imposing frequency and voltage. The reference voltage magnitude is used as additional control variable for the optimization algorithm. The loss function incorporates both the collection grid and the converter losses. The use of the proposed strategy results in an effective reduction of losses compared to conventional reactive power dispatch strategies alongside with improvements of the voltage profile. A case study for a 500 MW–sized WPP demonstrates an additional annual energy production of 6819 MWh or an economical benefit of 886 k€yr-1 when using the proposed strategy.Postprint (author's final draft

Methicillin-Susceptible Staphylococcus aureus Biofilm Formation on Vascular Grafts: an In Vitro Study

Staphylococcus aureus; Biofilm; InfectionStaphylococcus aureus; Biopelícula; InfecciónStaphylococcus aureus; Biopel·lícula; InfeccióThe aim of this study was to quantify in vitro biofilm formation by methicillin-susceptible Staphylococcus aureus (MSSA) on the surfaces of different types of commonly used vascular grafts. We performed an in vitro study with two clinical strains of MSSA (MSSA2 and MSSA6) and nine vascular grafts: Dacron (Hemagard), Dacron-heparin (Intergard heparin), Dacron-silver (Intergard Silver), Dacron-silver-triclosan (Intergard Synergy), Dacron-gelatin (Gelsoft Plus), Dacron plus polytetrafluoroethylene (Fusion), polytetrafluoroethylene (Propaten; Gore), Omniflow II, and bovine pericardium (XenoSure). Biofilm formation was induced in two phases: an initial 90-minute adherence phase and a 24-hour growth phase. Quantitative cultures were performed, and the results were expressed as log10 CFU per milliliter. The Dacron-silver-triclosan graft and Omniflow II were associated with the least biofilm formation by both MSSA2 and MSSA6. MSSA2 did not form a biofilm on the Dacron-silver-triclosan graft (0 CFU/mL), and the mean count on the Omniflow II graft was 3.89 CFU/mL (standard deviation [SD] 2.10). The mean count for the other grafts was 7.01 CFU/mL (SD 0.82). MSSA6 formed a biofilm on both grafts, with 2.42 CFU/mL (SD 2.44) on the Dacron-silver-triclosan graft and 3.62 CFU/mL (SD 2.21) on the Omniflow II. The mean biofilm growth on the remaining grafts was 7.33 CFU/mL (SD 0.28). The differences in biofilm formation on the Dacron-silver-triclosan and Omniflow II grafts compared to the other tested grafts were statistically significant. Our findings suggest that of the vascular grafts we studied, the Dacron-silver-triclosan and Omniflow II grafts might prevent biofilm formation by MSSA. Although further studies are needed, these grafts seem to be good candidates for clinical use in vascular surgeries at high risk of infections due to this microorganism. IMPORTANCE The Dacron silver-triclosan and Omniflow II vascular grafts showed the greatest resistance to in vitro methicillin-susceptible Staphylococcus aureus biofilm formation compared to other vascular grafts. These findings could allow us to choose the most resistant to infection prosthetic graft

PICO Questions and DELPHI Methodology for the Management of Venous Thromboembolism Associated with COVID-19

COVID-19; Anticoagulació; Malaltia tromboembòlica venosaCOVID-19; Anticoagulación; Enfermedad tromboembólica venosaCOVID-19; Anticoagulation; Venous thromboembolic diseasePatients with coronavirus disease 2019 (COVID-19) have a higher risk of venous thromboembolic disease (VTE) than patients with other infectious or inflammatory diseases, both as macrothrombosis (pulmonar embolism and deep vein thrombosis) or microthrombosis. However, the use of anticoagulation in this scenario remains controversial. This is a project that used DELPHI methodology to answer PICO questions related to anticoagulation in patients with COVID-19. The objective was to reach a consensus among multidisciplinary VTE experts providing answers to those PICO questions. Seven PICO questions regarding patients with COVID-19 responded with a broad consensus: 1. It is recommended to avoid pharmacological thromboprophylaxis in most COVID-19 patients not requiring hospital admission; 2. In most hospitalized patients for COVID-19 who are receiving oral anticoagulants before admission, it is recommended to replace them by low molecular weight heparin (LMWH) at therapeutic doses; 3. Thromboprophylaxis with LMWH at standard doses is suggested for COVID-19 patients admitted to a conventional hospital ward; 4. Standard-doses thromboprophylaxis with LMWH is recommended for COVID-19 patients requiring admission to Intensive Care Unit; 5. It is recommended not to determine D-Dimer levels routinely in COVID-19 hospitalized patients to select those in whom VTE should be suspected, or as a part of the diagnostic algorithm to rule out or confirm a VTE event; 6. It is recommended to discontinue pharmacological thromboprophylaxis at discharge in most patients hospitalized for COVID-19; 7. It is recommended to withdraw anticoagulant treatment after 3 months in most patients with a VTE event associated with COVID-19. The combination of PICO questions and DELPHI methodology provides a consensus on different recommendations for anticoagulation management in patients with COVID-19.This work was carried out with the institutional support and unconditional financial assistance of Sanofi, which had no role in the design, interpretation, or writing of the manuscript

Variation in the choice of elective surgical procedure for abdominal aortic aneurysm in Spain

Abdominal aortic aneurysm; Endovascular aneurysm repair; Open surgical repairAneurisma aòrtic abdominal; Reparació endovascular d'aneurismes; Reparació quirúrgica obertaAneurisma aórtico abdominal; Reparación endovascular de aneurismas; Reparación quirúrgica abiertaOBJECTIVE: The two main surgical treatments for abdominal aortic aneurysm (AAA) are open surgical repair (OSR) and endovascular aneurysm repair (EVAR). The aim of this study was to analyze variation among Spanish hospitals in the use of OSR or EVAR for AAA. A secondary aim was to assess changes in preferences for these two procedures over time. METHODS: This was a retrospective longitudinal study based on discharge data from public hospitals in Spain during 2002-2012. Patient inclusion criteria were: age >18 years, elective admission, primary diagnosis of unruptured AAA, and surgical treatment with OSR or EVAR. The characteristics of the treating center, patients, and in-hospital mortality were recorded. RESULTS: We included 16,737 patients from 114 hospitals; 6,809 (40.7%) underwent EVAR and 9,928 (59.3%) underwent OSR. The total volume of surgeries increased throughout the period, and the probability that any given procedure was EVAR increased by 20% per year (OR 1.20, P<0.001). The volume and distribution of the two procedures varied highly across the participating hospitals. Overall, in-hospital mortality rate was 3.6% and it decreased during the study period (5.3% in 2002 and 3.2% in 2012), mainly due to a decrease in OSR-related mortality, despite a slight increase in EVAR-related mortality. Hospitals with higher surgical volumes were more likely to use EVAR and have lower in-hospital mortality rates. CONCLUSION: This study reveals high variability in the surgical treatment of unruptured AAA across Spanish hospitals. The number of interventions has increased in recent years, with EVAR accounting for a growing percentage of these surgical procedures. Overall in-hospital mortality rates decreased significantly during this period, mainly due to lower mortality among patients undergoing OSR. In-hospital mortality rates were lower in higher-volume centers, regardless of the surgical approach used. Further research on variability and appropriateness of surgical management of AAA is required to assess the suitability of concentrating elective AAA repair in more experienced centers to potentially achieve better outcomes

Systematic review of the results of kidney transplantation in patients with aortoiliac revascularization surgery

Enfermedad renal crónica; Trasplante renal; Cirugía de revascularizaciónChronic kidney disease; Kidney transplantation; Revascularization surgeryMalaltia renal crònica; Trasplantament renal; Cirurgia de revascularitzacióIntroducción: la enfermedad renal crónica (ERC) acelera el proceso de arterioesclerosis, lo que incrementa la prevalencia de enfermedad arterial periférica (EAP). El objetivo de esta revisión sistemática es evaluar los resultados del trasplante renal en pacientes sometidos a cirugía abierta de revascularización del sector aortoilíaco por arteriopatía crónica de las extremidades inferiores. Material y métodos: revisión sistemática según las recomendaciones QUOROM de artículos en PubMed y Cochrane, en español e inglés, que incluían pacientes con ERC y cirugía abierta de revascularización del sector aortoilíaco en el pasado o como indicación previa a un trasplante renal. Los artículos incluidos describían complicaciones inmediatas, supervivencia del injerto y supervivencia del paciente después del trasplante renal. Resultados: la búsqueda generó 253 artículos. Tras la revisión se seleccionaron 8 artículos que incluían 101 pacientes, de los que el 84,2 % fueron trasplantados. La incidencia de complicaciones tras la revascularización fue del 25,9 % y la incidencia de complicaciones tras el trasplante renal fue del 28,2 %. La mediana de seguimiento fue de 22 meses (rango: 6,7 a 71). La supervivencia del injerto renal fue del 80 % y la del paciente fue del 90,5 % al final del seguimiento. Conclusión: la coexistencia de enfermedad arterial y renal no debe considerarse un obstáculo para la realización de un trasplante renal. Los datos publicados hasta el momento muestran resultados satisfactorios en la supervivencia del injerto y del paciente.Introduction: chronic kidney disease (CKD) increases and accelerates the arterial calcification process, increasing the prevalence of peripheral arterial disease in these patients. The aim of this systematic review is to evaluate the results of kidney transplantation in patients who have undergone open revascularization surgery in the aorto-iliac sector for chronic lower limb arteriopathy. Material and methods: systematic review, following QUORUM recommendations, of articles in PubMed and Cochrane, in English or Spanish, which include patients with CKD, who have undergone open revascularization surgery of the aorto-iliac sector in the past or as a prior indication to kidney transplantation. Articles included described immediate complications, graft survival and patient survival after kidney transplantation. Results: the search generated 253 articles and after the systematic review, 8 articles that included, 101 patients were selected, 84.2 % of whom were transplanted. Complications of revascularization surgery were 25.9 % and complications of kidney transplantation were 28.2 %. Median follow-up was 22 months (range: 6.7 to 71). Graft survival was 80 % and patient survival was 100 % at the end of follow-up. Conclusion: the coexistence of vascular and kidney disease should not be an obstacle to performing a kidney transplantation. Since the data published so far shows satisfactory results in graft and patient survival

Estudio coste efectividad del proceso diagnóstico de la trombosis venosa profunda desde la atención primaria

Analizar el coste-efectividad de la aplicación de algoritmos diagnósticos en pacientes con sospecha de un primer episodio de trombosis venosa profunda (TVP) en la atención primaria, en comparación con la derivación sistemática a centros especializados. Estudio observacional, transversal y analítico. Pacientes seleccionados en urgencias hospitalarias derivados desde la atención primaria para completar estudio y diagnóstico. Se reclutó a 138 candidatos con clínica compatible con un primer episodio de TVP; 22 fueron excluidos (sin informe de derivación, clínica de más de 30 días, anticoagulados y TVP previa), incluyéndose finalmente a 116 pacientes, un 61% mujeres, de 71 años edad media. Variables de las escalas de probabilidad clínica de Wells y Oudega, dímero-D (portátil y hospitalario), ecografía-Doppler y costes directos generados por los 3 circuitos analizados: derivación sistemática de todos los pacientes, derivación según escala de Oudega o de Wells. En el 18,9% se confirmó el diagnóstico de TVP. Las 2 escalas de probabilidad clínica presentaron una sensibilidad del 100% (IC del 95%: 85,1-100) y una especificidad alrededor del 40%. Con la aplicación de las escalas, se hubiesen podido evitar con total seguridad un tercio de las derivaciones a urgencias hospitalarias (p < 0,001) y se hubieran podido disminuir los costes del proceso diagnóstico en 8.620 € según Oudega y 9.741 € según Wells, por cada 100 pacientes atendidos. La aplicación de algoritmos diagnósticos en las sospechas de TVP permitiría al médico de atención primaria una orientación más resolutiva y coste-efectiva del proceso diagnóstico

Comparison of resistive capacitive energy transfer therapy on cadaveric molars and incisors with and without implants.

Capacitive-resistive energy transfer therapy (CRet) is used to improve the rehabilitation of different injuries. This study aimed to evaluate and compare the changes in temperature and current flow during different CRet applications on upper and lower molars and incisors, with and without implants, on ten cryopreserved corpses. Temperatures were taken on molars and incisors with invasive devices and skin temperature was taken with a digital thermometer at the beginning and after treatments. Four interventions: 15 VA capacitive hypothermic (CAPH), 8 watts resistive (RES8), 20 watts resistive (RES20) and 75 VA capacitive (CAP75) were performed for 5 min each. All treatments in this study generated current flow (more than 0.00005 A/m2) and did not generate a significant temperature increase (p > 0.05). However, RES20 application slightly increased surface temperature on incisors without implants (p = 0.010), and molar with (p = 0.001) and without implant (p = 0.008). Also, CAP75 application increased surface temperature on molars with implant (p = 0.002) and upper incisor with implant (p = 0.001). In conclusion, RES8 and CAPH applications seem to be the best options to achieve current flow without an increase in temperature on molars and incisors with and without implants