59 research outputs found
Etudes Raman d’encres de nanotubeset de graphene monofeuillets
No full textNational audienceNous discutons les signatures Raman de nanotubes de carbone monofeuillets (single-wall carbon nanotubes,SWNT) et de feuillets de graphène monofeuillets (single layer graphene, SLG) dispersés dans l’eau (fig. 1) et leurorigine physique. Les encres de SWNT sont stabilisées avec des tensio-actifs. Les études optiques dans le procheinfrarouge permettent de mesurer simultanément le signal Raman et le signal de photoluminescence caractéristiquedes nanotubes dispersés à l’échelle individuelle (fig. 2, gauche). Le signal de PL est sensible à l’environnementdiélectrique des nanotubes et permet d’étudier les interactions avec le tensio-actif [1]. A fortes concentrations, lesSWNT forment des phases cristal liquide et l’étude de la polarisation des signaux Raman/PL conduit à la mesure du paramètre d’ordre orientationnel [2]. Les encres de SWNT peuvent être déposées par jet d’encre, les textures des dépôts et leur conductivité électrique dépendent de la concentration des encres [3]. Des encres de graphène SLG, baptisées ‘‘eau de graphène’’ peuvent être préparées sans tensioactif en dispersant despolyélectrolytes de SLG dans de l’eau dégazée [4]. Les signatures Raman des SLG dispersées dans l’eau sontvoisines de celles des SLG suspendues dans l’air (fig. 2), avec des décalages modérés des bandes principales quisont discutées en terme de dopage et de contraintes mécaniques [5]. Les défauts ponctuels observés sur les SLG dispersées dans l’eau peuvent être facilement éliminés par un recuit des dépôts à 800°C. References [1] F. Torres-Cañas et al, J. Phys. Chem. C 119 (2015), pp. 703-709 [2] C. Zamora-Ledezma et al, J. Phys. Chem. C 115 (2011), pp. 3272-3278 [3] F. Torres-Cañas et al, Mat. Res. Exp. 4 (2016) [4] G. Bepete et al, Nature Chem. 9 (2016), pp. 347-352 [5] G. Bepete et al, J. Phys. Chem. C 120 (2016), pp. 28204-28214 <BR
An investigation of shock-induced phase transition in soda-lime glass
No full textThere exists a large body of evidence from experiments and molecular dynamics simulations to suggest the occurrence of phase transitions in soda-lime glass (SLG) and other silica glasses subject to shock compression to pressures above 3 GPa. In light of these findings, the current work investigated the existence of phase transition in SLG using shock and release experiments. The experiments employed symmetric SLG-SLG impact to achieve complete unloading to zero stress after shock compression to stresses in the range of 3-7 GPa. The stress-strain response and the Lagrangian release wave speed behavior of SLG obtained from these experiments are seen to reveal a mismatch between the loading and unloading paths of the pressure-strain curve for the material, which serves as compelling evidence for the occurrence of a shock-induced phase transition in the material at relatively low pressures. Furthermore, the release wave speed vs strain data obtained from experiments were used to construct a methodology for modeling the shock and release behavior of SLG. This scheme implemented in numerical simulations was able to capture the release behavior of shock compressed SLG, for which a robust and satisfactory model was previously unavailable.</p
Valor del strain longitudinal global como factor predictor de reingreso hospitalario en pacientes con insuficiencia cardiaca aguda atendidos en el Hospital Nacional Edgardo Rebagliati Martins durante el periodo 2022-2023, Lima – Perú
No full textEl estudio busca determinar si existe una asociación entre el valor del Strain Longitudinal Global (SLG) y el
reingreso hospitalario en pacientes con insuficiencia cardíaca aguda en el Hospital Nacional Edgardo
Rebagliati Martins durante el período 2022-2023.
Objetivos: Establecer el valor del SLG en pacientes con insuficiencia cardíaca aguda atendidos en el hospital.
Determinar la incidencia de reingresos en pacientes con esta condición dentro de los primeros 6 meses post alta.
Identificar un punto de corte del SLG que esté relacionado con un mayor riesgo de reingreso en el mismo período.
Metodología: Estudio de cohorte, observacional, longitudinal y prospectivo. Población: Pacientes mayores de 18
años diagnosticados con insuficiencia cardíaca aguda en el hospital entre abril de 2022 y octubre de 2023.
Muestra: Se incluirá el 100% de los pacientes que cumplan con los criterios de criterios de inclusión y exclusión:
Inclusión: Pacientes mayores de 18 años hospitalizados con diagnóstico de insuficiencia cardíaca. exclusión:
Pacientes con imágenes inadecuadas para calcular el SLG, diagnósticos de SCA, cardiopatías congénitas,
transferencias a otros hospitales o que no deseen participar. Recolección de datos: Se utilizará una ficha de
recolección que incluirá parámetros clínicos y ecocardiográficos, validada por expertos. Se aplicará estadística
descriptiva para caracterizar a los pacientes. Se utilizarán pruebas estadísticas adecuadas para comparar
variables y ajustar modelos de regresión de Cox para evaluar el SLG como predictor independiente < 0.05
de reingreso hospitalario. Se considerará un valor de p como significativo. Este estudio busca contribuir
al entendimiento de cómo el SLG puede predecir reingresos hospitalarios, lo cual es crucial para mejorar
la atención y el manejo de pacientes con insuficiencia cardíaca agudaSubmitted by Ernesto Rojas ([email protected]) on 2024-09-13T20:04:20Z
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T030_74134609_S VILLANUEVA GARCIA, ERIK JOSEPH.pdf: 613907 bytes, checksum: 764cfef9aec95809c656d0911d6185e2 (MD5)Made available in DSpace on 2024-09-13T20:04:20Z (GMT). No. of bitstreams: 1
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Previous issue date: 2024Tesi
Enhanced conduction and pool boiling heat transfer on single-layer graphene-coated substrates
No full textMolecular dynamics simulations were employed to understand the improved thermal conductivity and water boiling heat transfer characteristics of adding single-layer graphene (SLG) to substrates. The 100, 110, and 111 planes of Cu, Ni, Pt, and Si were selected for study based on common heat transfer and graphene-compatible materials. Vibrational density of states data was analyzed in order to view heat flux trends. After equilibration at 300K the temperature was increased to 400K for 3 ns to induce nucleate boiling (~27K wall superheat). It was found that the addition of SLG greatly improved the overall thermal conductivity of the composite substrate, with increases in the 1-2 orders of magnitude range. The temperature gradients for SLG-coated substrates were found to be much lower than bare substrates. Nanoscale boiling curves were produced. The CuG100 case shows a 14% increase in critical heat flux (CHF) (~0.36 GW/m2) over the Cu100 case, and the PtG100 shows a 9% increase (~0.48 GW/m2) over the Pt100 case. The SLG-coated substrates also required less superheat to achieve the CHF condition.Peer reviewe
Análise de componentes principais e contribuições das variáveis e estações meteorológicas na determinação da evapotranspiração de referência no Estado do Rio Grande do Sul
No full textReference evapotranspiration (ETo) is fundamental in hydrology and meteorology, and is widely used in climate change prediction and land use. This study used principal component analysis (PCA) to determine the contributions of meteorological variables and stations in estimating ETo, employing daily data from thirteen meteorological stations in the State of Rio Grande do Sul from 1990 to 2022, categorized by seasonal periods. The first three principal components explained 85.6% of the total ETo variability in spring, 87.9% in summer, 81.5% in autumn and 80.4% in winter. Tmax, RHmin and Rs were the most significant meteorological variables in spring, summer and autumn, while u2 and Rs stood out in winter. The stations with the largest contributions were: Uruguaiana, Bom Jesus, Torres, São Borja and SLG in spring and summer; Bom Jesus, Encruzilhada - Canguçu, São Borja and SLG (autumn); and Camaquã, Passo Fundo, Porto Alegre and Torres in winter. These results provide accurate information on the meteorological variables and seasons that influence ETo, highlighting climate variability on seasonal scales and contributing to an adequate representation of regional water demand.La evapotranspiración de referencia (ETo) es fundamental en hidrología y meteorología, y se utiliza en la predicción del cambio climático y el uso del suelo. Este estudio utilozó el análisis de componentes principales (PCA) para determinar las contribuciones de las variables meteorológicas y las estaciones en la estimación de ETo, empleando datos diarios de trece estaciones meteorológicas del Estado de Rio Grande do Sul entre 1990 y 2022, categorizados por períodos estacionales. Los primeros tres componentes principales explicaron el 85,6% de la variabilidad total de la ETo en primavera, el 87,9% en verano, el 81,5% en otoño y el 80,4% en invierno. Tmax, HRmin y Rs fueron las variables meteorológicas más significativas en primavera, verano y otoño, mientras que u2 y Rs destacaron en invierno. Las estaciones con mayores contribuciones fueron: Uruguaiana, Bom Jesus, Torres, São Borja y SLG (primavera y verano); Bom Jesus, Encruzilhada - Canguçu, São Borja y SLG (otoño); y Camaquã, Passo Fundo, Porto Alegre y Torres (invierno). Estos resultados proporcionan información precisa sobre las variables meteorológicas y las estaciones que influyen en la ETo, destacando la variabilidad climática en escala estacional y contribuyendo a una representación adecuada de la demanda regional de agua.A evapotranspiração de referência (ETo) é fundamental na hidrologia e meteorologia, sendo amplamente utilizada na previsão de alterações climáticas e no uso da terra. Este estudo utilizou a análise de componentes principais (PCA) para determinar as contribuições das variáveis e estações meteorológicas na estimativa da ETo, utilizando com dados diários de treze estações meteorológicas no Estado do Rio Grande do Sul de 1990 a 2022, segregados por períodos sazonais. As três primeiras componentes principais explicaram 85,6% da variabilidade total da ETo na primavera, 87,9% no verão, 81,5% no outono e 80,4% no inverno. Tmax, RHmin e Rs foram as variáveis meteorológicas mais significativas na primavera, verão e outono, enquanto u2 e Rs se destacaram no inverno. As estações com maiores contribuições foram: Uruguaiana, Bom Jesus, Torres, São Borja e SLG (primavera e verão); Bom Jesus, Encruzilhada - Canguçu, São Borja e SLG (outono); e Camaquã, Passo Fundo, Porto Alegre e Torres (inverno). Esses resultados fornecem informações precisas sobre as variáveis e estações meteorológicas que influenciam a ETo, evidenciando a variabilidade climática em escalas sazonais e contribuindo para uma representação adequada da demanda hídrica regional
Photovoltaic performance of non-covalent functionalized single-layer graphene in dye-sensitized solar cells (DSSCs)
No full textIn this study, it was aimed to fabricate new effective alternative counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). For this purpose, firstly, single-layer graphene (SLG) thin films were grown by chemical vapor deposition (CVD) method. Then, these films were separately functionalized with 1,8-cineole (ppCin/SLG), D-Limonene (ppLim/SLG) and Thiophene (ppTh/SLG) by plasma polymerization. Number of layers in CVD-grown graphene determined by Raman, transmission electron microscope (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. Chemical structures of plasma polymerised (pp) thin films were investigated by Fourier transform infrared (FTIR) spectroscopy. Photovoltaic parameters of DSSCs were calculated, and electrocatalytic properties of CEs were investigated by electrochemical impedance spectroscopy (EIS). Polymer functionalization greatly enhanced the electrical conductivity and electrocatalytic activity properties of graphene compared to that of SLG. The efficiencies of DSSCs with ppCin/SLG and ppLim/SLG CEs were 1.10% and 1.02%, respectively. As a result, the cell efficiencies of ppCin/SLG and ppLim/SLG could be as alternative materials to platinum (Pt) counter electrode.Ataturk university [BAP/2016-176]The author is grateful to NANOVAK Company (Ankara, TURKEY) for all kinds of technical support. We would like to thank Cagri Cirak for his support in photovoltaic performance analysis. The authors thankfully acknowledge the financial support by research fund of Ataturk university (Project Numbers: BAP/2016-176)
A 17-year surgical experience of the intraoral approach for ranulas
No full textInternational audienceBACKGROUND: The aim of this study was to analyze the clinical features and treatment outcomes in order to determine the optimal management of ranulas in our Oral and Maxillofacial Surgery department with long-term results.METHODS: A retrospective study was performed to evaluate patients with a final diagnosis of a simple or plunging ranula at Lille Teaching Hospital from May 2000 to January 2017. Clinical data on ranulas that were reviewed included gender, age, symptoms, location of the lesion, surgical procedures, complications, recurrence and follow-up.RESULTS: The 26 patients included in the study comprised 18 males and 8 females, ranging from 3-months to 38 years of age. A total of 27 ranulas were managed: 25 oral ranula and 2 plunging ranulas. Twelve patients had undergone marsupialization (44.4%), 7 patients had complete excisions of the ranula (25.9%) or partial excisions combined with marsupialization (14.8%) and 4 patients (14.8%) had undergone excision of the sublingual gland (SLG). Seven ranulas recurred (25.9%). Not a single case recurred following the excision of the SLG. Treatments that included marsupialization were associated with the lowest recurrence rate (16.7%) after SLG excision, followed by combined marsupialization and ranula excision (25%) and by ranula excision alone (57%). There were no major complications.CONCLUSIONS: Long-term outcomes confirm the different surgical procedures available in the outpatient clinic for the management of ranulas based on our surgical experience. Transoral resection of the SLG should be the optimal treatment, producing the lowest recurrence rate
Wafer-scale transfer-free process of multi-layered graphene grown by chemical vapor deposition
No full textChemical vapour deposition (CVD) has emerged as the dominant technique to combine high quality with large scale production of graphene. The key challenge for CVD graphene remains the transfer of the film from the growth substrate to the target substrate while preserving the quality of the material. Avoiding the transfer process of single or multi-layered graphene (SLG-MLG) has recently garnered much more interest. Here we report an original method to obtain a 4-inch wafer fully covered by MLG without any transfer step from the growth substrate. We prove that the MLG is completely released on the oxidized silicon wafer. A hydrogen peroxide solution is used to etch the molybdenum layer, used as a catalyst for the MLG growth via CVD. X-ray photoelectron spectroscopy proves that the layer of Mo is etched away and no residues of Mo are trapped beneath MLG. Terahertz transmission near-field imaging as well as Raman spectroscopy and atomic force microscopy show the homogeneity of the MLG film on the entire wafer after the Mo layer etch. These results mark a significant step forward for numerous applications of SLG-MLG on wafer scale, ranging from micro/nano-fabrication to solar cells technology.Electronic Components, Technology and MaterialsChemE/O&O groe
Clinical and Anatomic Study on the Ducts of the Submandibular and Sublingual Glands
No full textPurpose: To investigate the relationship between the ducts of the submandibular gland (SMG) and sublingual gland (SLG) and discuss its clinical application relating to SMG radiologic examinations and transfer. Materials and Methods: The microanatomy of the SMG and SLG was investigated by use of 30 adult cadavers through anatomic dissection by use of a microscope. The relationship between the SMG and SLG ducts was observed and recorded during operations of microvascular autologous SMG transfer in 63 cases of severe keratoconjunctivitis sicca. Results: There were 3 patterns of SLG and SMG duct anatomic variation: 1) The SMG and SLG have their own respective ducts that secrete separately at the orifices of the ducts in the floor of the mouth. 2) The SLG has a major duct that joins the duct of the SMG. 3) The SLG only has many fine ducts (7-15) that secrete in the floor of the mouth. Conclusions: The anatomy of the ducts of the SMG and SLG is quite complicated. More attention should be paid to the anatomy of the ducts during surgery or imaging procedures related to the SMG. Crown Copyright © 2010.link_to_subscribed_fulltex
Effects of Surface Modifications to Single and Multilayer Graphene Temperature Coefficient of Resistance
No full text© 2020 American Chemical Society. Interfacial effects on single-layer graphene (SLG) or multilayer graphene (MLG) properties greatly affect device performance. Thus, the effect of the interface on the temperature coefficient of resistance (TCR) on SLG and MLG due to surface-deposited core-shell metallic nanoparticles (MNPs) and various substrates was experimentally investigated. Observed substrates included glass, SiO2, and Si3N4. We show that these modifications can be used to strongly influence SLG interface effects, thus increasing the TCR up to a 0.456% per K resistance change when in contact with the SiO2 substrate at the bottom surface and MNPs on the top surface. However, these surface interactions are muted in MLG due to the screening effect of nonsuperficial layers, only achieving a -0.0998% per K resistance change in contact with the bottom Si3N4 substrate and the top MNPs. We also demonstrate contrary thermal sensitivity responses between SLG and MLG after the addition of MNP to the surface11Nsciescopu
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