First stage in flash sintering of zirconia based ceramics

Flash sintering ability to densify ceramic material in less than 5 seconds, at much lower furnace temperatures than conventional sintering has been reported and studied for a large set of conductive ceramics and recently of composite ceramic materials. Since no die is used, the current mandatorily flows through the sample and the flash process is characterized by an abrupt increase in the sample conductivity accompanied by shrinkage and densification. In the literature two types of experiments are reported, referring to the furnace temperature: Constant heating rate (CHR) and isothermal experiments. The flash sintering elementary mechanisms are not yet fully understood. It has been recognized that, in isothermal experiments, the flash densification stage (“flash stage”) is observed after an incubation period during which no macroscopic densification is observed (“pre-flash stage”, or first stage); and in the CHR experiments, the densification temperature varies according to the intensity of the applied electric field. According to the literature and to our previous works, the effective electrical conductivity of the sample is a key parameter of the flash effect. In the present work, this parameter was varied using conducting/insulating ceramic composites with different amounts of insulating phase. This presentation reports and analyses the result of a study on the effect of a non-conductive second phase, alumina, on the first stage of the flash sintering of zirconia based ceramics in both CHR and isothermal furnace experiments. Spray dried 8 mol% Y2O3 zirconia (from Tosoh) and alumina - 3 mol% Y2O3 zirconia powder blends provided by Baikowski Company were used, with alumina volume fraction ranging from 0 to 60%, enabling a wide range of effective conductivity values. In the CHR experiments samples were heated from 20 to 1500°C at 10°C/min and the electric field was applied from 500°C. In this case, the flash temperature is the experimental macroscopic analyzed result. For the isothermal experiments, the samples were preheated at different temperatures T0 (900 to 1400°C) before applying the electric field. In this case the delay time (or incubation time) to observe the flash event is the experimental macroscopic analyzed observation. All experiments were performed under constant AC (1kHz) electric field E0, with E0 of 100 and 200V/cm. The sample electrical conductivity was measured by impedance spectroscopy and recorded during all the sintering cycle. Regarding the pre-flash period, our results show that the flash event is related to sample conductivity (which is determined by the amount of non-conductive phase) in both CHR and isothermal experiments. The data analysis for both types of experiments shows that the flash conditions are determined by a balance between the electric power supplied to the sample and the heat losses. Experimental data are in agreement with a thermal process in which the internal Joule dissipation heating competes with external heat losses. A simple model is proposed on this basis, which predicts the experimentally observed scaling laws. The observation of alumina-zirconia eutectic microstructures in flash sintered composite samples and microstructure evolution of 8YSZ powder confirms that internal sample temperatures reached during the flash are in agreement with the temperature estimations obtained from the recorded conductivity evolution

Relaciones interpersonales y desempeño laboral del profesional de enfermería del servicio de emergencias de un Hospital Nacional 2020

Las relaciones interpersonales son sumamente importantes para mantener un entorno laboral saludable de armonía y, sobre todo, en el trabajo de equipo de los enfermeros porque favorece el desempeño laboral en las áreas críticas para la comunicación efectiva en beneficio del cuidado del paciente. Objetivo: Determinar la relación entre las relaciones interpersonales y el desempeño laboral del Profesional de Enfermería del Servicio de Emergencias de un Hospital Nacional – 2020. Metodología: Estudio enfoque cuantitativo, correlacional, de diseño no experimental y de corte transversal. Población estuvo conformada por el total de 76 enfermeras que laboran en el servicio de emergencias. Se aplicó dos instrumentos: Escala de Relaciones Interpersonales el cual consta de 3 dimensiones: comunicación, actitudes, trato con 18 ítems y Desempeño Laboral cuestionario que consta de 3 dimensiones: aspectos ligados a la gestión, aspectos ligados a la productividad, aspectos ligados a la persona, con 16 ítems ambos instrumentos se miden con una escala de Likert y fueron validados por expertos y sometido la prueba piloto donde su confiabilidad del Alfa de Cronbach fue de 0.72 y 0.76. Los resultados obtenidos fueron que las relaciones interpersonales y el desempeño laboral tuvieron una relación baja (r=0,098), y las relaciones interpersonales y las dimensiones del desempeño laboral sus valores fueron (r=0,108, r=0,70 y r=018) respectivamente. Se concluye que no existe una correlación entre las relaciones interpersonales con el desempeño laboral del profesional de enfermería es probable que estos resultados se deban que por las exigencias del servicio en la unidad de emergencia hace que las relaciones entre ellas son dejadas de lado. Se concluye que no existe una correlación entre las relaciones interpersonales con el desempeño laboral del profesional de enfermería es probable que estos resultados se deban por las exigencias, carencias y la complejidad de los casos que llegan a diario en la unidad de emergencia y hace que las relaciones entre ellas no son priorizadas a pesar de su importancia y sus beneficios

Catalytic dense membranes of doped Bi4V2O11 (BIMEVOX) for selective partial oxidation: chemistry of defects versus catalysis

A catalytic dense membrane reactor (CDMR) is used to physically separate the reaction step from the reoxidation of the catalyst. By decoupling the redox mechanism prevailing in mild oxidation of hydrocarbons, the operating conditions may be optimized resulting in an increase of selectivity. The membranes are made up of BIMEVOX oxides, obtained by partial substitution of V in Γ-Bi4V2O11 by ME (Co, Cu, Ta). Experiments performed on BIMEVOX dense membranes using propene and propane are described in terms of, (i) active sites on polished or unpolished surfaces, (ii) operating conditions (T, pO2 in the high oxygen partial pressure compartment), which determine the selectivity, either to mild oxidation products (acrolein, hexadiene, CO), or to partial oxidation products (CO, H2), and, (iii) nature of ME cations and relative properties. The discussion deals with the respective role of electronic vs. oxide ion conductivities which depend on defects in the structure as well as on the redox properties of cations

Elusa. From Nabatean Trading Post to Late Antique Desert Metropolis: Results of the 2015−2020 Seasons

In Roman to late Byzantine times, Elusa (Hebrew: Haluza, Arabic: al-Khalasa) was the most important settlement in the Negev region and its only proper city. Identified in 1838 by E. Robinson, it was subsequently visited by numerous researchers. The most important investigations took place in the form of surveys and excavations from the 1970s until 2001, during which, among other things, the only theatre in the region and the city’s cathedral were uncovered. However, despite several research projects, very basic information on the city and its genesis, history and structure has been lacking until now. Since 2015, this has been the focus of an international cooperation project that is investigating these fundamental questions using a multi-method approach. The focus here is also on the role of the city in the region, as it appears as an economic, administrative, cultural and religious centre. Particular emphasis is placed on the city’s flourishing in light of its precarious natural location within the Negev Desert. The article reflects the combined findings of remote sensing, archaeological survey, geophysical prospection, targeted excavations, geochemical soil sampling and extensive find material analyses and thus provides an unprecedented insight into the character and development of ancient Elusa.In Roman to late Byzantine times, Elusa (Hebrew: Haluza, Arabic: al-Khalasa) was the most important settlement in the Negev region and its only proper city. Identified in 1838 by E. Robinson, it was subsequently visited by numerous researchers. The most important investigations took place in the form of surveys and excavations from the 1970s until 2001, during which, among other things, the only theatre in the region and the city’s cathedral were uncovered. However, despite several research projects, very basic information on the city and its genesis, history and structure has been lacking until now. Since 2015, this has been the focus of an international cooperation project that is investigating these fundamental questions using a multi-method approach. The focus here is also on the role of the city in the region, as it appears as an economic, administrative, cultural and religious centre. Particular emphasis is placed on the city’s flourishing in light of its precarious natural location within the Negev Desert. The article reflects the combined findings of remote sensing, archaeological survey, geophysical prospection, targeted excavations, geochemical soil sampling and extensive find material analyses and thus provides an unprecedented insight into the character and development of ancient Elusa

Estereotipos de género y sexismo ambivalente en estudiantes que pertenecen a universidades ubicadas en el distrito de Los Olivos, 2021

El objetivo de la presente investigación es determinar la relación entre los estereotipos de género y sexismo ambivalente en estudiantes que pertenecen a universidades ubicadas en el distrito de Los Olivos, 2021. El tipo de investigación es de básica, correlacional ya que busca relación entre dos variables y de corte transversal. La muestra estuvo conformada por 369 estudiantes universitarios, de ambos sexos, matriculados en universidades que se encuentren en el distrito de Los Olivos. La técnica empleada fue la encuesta, contando como instrumentos de recolección de datos el Cuestionario de estereotipos de género y el Inventario de sexismo ambivalente. En los resultados, se observa que existe una correlación significativa (p = ,000) de manera que es positiva muy fuerte entre ambas variables (Rho = ,761). Asimismo, estadísticamente presentan una correlación positiva considerable entre las dimensiones de sexismo ambivalente y estereotipos de género

Relationship between humoral response against hepatitis C virus and disease overcome

International audienceConclusionHumoral response against hepatitis C virus linear epitopes is partly modified according to the disease state. This study highlights the importance of considering relative quantities of antibodies with different specificities rather than the amount of each antibody.Hepatitis C virus infection leads to liver disease whose severity can range from mild to serious lifelong illness. However the parameters involved in the evolution of the disease are still unknown. Among other factors, the virus-elicited antibody profile is suspected to play a role in the outcome of the disease. Analysis of the relationship between anti-virus antibodies and disease state requires the analysis of a large number of serums from patients (hepatitis C virus+) and of epitopes from the viral proteins. Such a study would benefit from microarray-based screening systems that are appropriate for high-throughput assays.We used a method combining peptide chips and surface plasmon resonance imaging previously shown to be suitable for analyzing complex mediums and detecting peptide-protein interactions. 56 peptides covering the entire viral proteome were grafted on chips and their interaction with antibodies present in the 68 injected serums from infected and non-infected donors was measured. Statistical analyses were conducted to determine a possible relationship between antibodies (specificity and amount) and disease states.A good discrimination between infected and non-infected donors validated our approach, and several correlations between antibodies profiles and clinical parameters have been identified. In particular, we demonstrated that ratios between particular antibodies levels allow for accurate discrimination of patients according to their pathologic states

New criteria for the molecular identification of cereal grains associated with archaeological artefacts.

The domestication and transmission of cereals is one of the most fundamental components of early farming, but direct evidence of their use in early culinary practices and economies has remained frustratingly elusive. Using analysis of a well-preserved Early Bronze Age wooden container from Switzerland, we propose novel criteria for the identification of cereal residues. Using gas chromatography mass spectrometry (GC-MS), we identified compounds typically associated with plant products, including a series of phenolic lipids (alkylresorcinols) found only at appreciable concentration in wheat and rye bran. The value of these lipids as cereal grain biomarkers were independently corroborated by the presence of macrobotanical remains embedded in the deposit, and wheat and rye endosperm peptides extracted from residue. These findings demonstrate the utility of a lipid-based biomarker for wheat and rye bran and offer a methodological template for future investigations of wider range of archaeological contexts. Alkylresorcinols provide a new tool for residue analysis which can help explore the spread and exploitation of cereal grains, a fundamental component of the advent and spread of farming

The Basel-Gasfabrik research project: Addressing complex topics by an integrative approach

The late La Tène period site of Basel-Gasfabrik has been under investigation for more than a century. During that time, the unfortified settlement with its two cemeteries has yielded huge amounts of everyday and exceptional objects and features. Beginning in the mid-1970s, samples were systematically collected for scientific analyses during ongoing excavations, thus producing ideal preconditions for interdisciplinary research. In 2011-2014, the international research project “Approaching the living via the dead: human remains from the Late La Tène site Basel-Gasfabrik and their cultural-historical interpretations” addressed the multifarious ways in which the Iron Age community handled their deceased. The intense collaboration involved researchers from the Archäologische Bodenforschung Basel-Stadt and the universities of Basel (CH), Mainz and Freiburg i.Br. (D) and spanned eight disciplines: archaeology, archeoanthropology, archaeobotany, archaeozoology, geoarchaeology, biogeochemistry, molecular genetics and statistics. Research topics and theoretical frameworks were developed jointly as well as procedures to combine the disciplinary results in multistage processes in order to generate integrative syntheses of novel insights. The challenges and specific research potentials of the integrative approach may serve as a positive example for future interdisciplinary research project