Wire and arc additive manufacturing (WAAM) enables the building of near net-shape components layer by layer by using arc welding technologies and wire filler metal as feedstock. The study aims at ...comparing the applicability of two innovative robotic arc welding technologies (cold metal transfer (CMT) and TopTIG) for additive manufacturing (AM) of stainless steel parts. Initially, a process development has been completed with the goal of optimizing material deposition rate during arc time. Both continuous and pulsed current programs were implemented. Then, different thick-walled samples composed of more than one overlapped weld bead per layer were manufactured in 316L stainless steel grade by CMT and TopTIG. Mechanical properties have been determined in as-build samples in different building orientations. WAAM applying CMT and TopTIG welding technologies is analyzed in terms of part quality (defined as the absence of defects such as pores, cracks, and/or lack of fusion defects); surface finishing; part accuracy; productivity; microstructural characteristics; and mechanical properties. Achieved mechanical properties and deposition rates are compared with the state of the art. Findings and conclusions of this work are applicable to the industrial manufacturing of stainless steel parts and requirements to apply these technologies to other expensive materials are finally discussed.
► High rotation speed yielded intense onion ring-like mixing pattern in the stir zone. ► Limited material mixing at low rotation speeds. ► Pin tool threaded profile plays an important role in ...material flow and mixing pattern.
The scope of this investigation is to evaluate the effect of joining parameters on the mechanical properties, microstructural features and material flow of dissimilar aluminium alloys (3mm-thick AA2024-T3 and AA7075-T6 sheets) joints produced by friction stir welding. Mechanical performance has been investigated in terms of hardness and tensile testing. Material flow using the stop action technique has also been investigated in order to understand the main features of the mixing process. No onion ring formation has been observed; the boundary between both base materials at the stir zone is clearly delineated, i.e., no material mixing is observed. A non-stable rotational flow inside the threads has been identified due to the formation of a cavity on the rear of the pin. Microstructural observation has revealed the development of a recrystallised fine-grained stir zone, with two different grain sizes resulting from the two different base materials.
The clinical course of COVID-19 critically ill patients, during their admission in the intensive care unit (UCI), including medical and infectious complications and support therapies, as well as ...their association with in-ICU mortality has not been fully reported.
This study aimed to describe clinical characteristics and clinical course of ICU COVID-19 patients, and to determine risk factors for ICU mortality of COVID-19 patients.
Prospective, multicentre, cohort study that enrolled critically ill COVID-19 patients admitted into 30 ICUs from Spain and Andorra. Consecutive patients from March 12
to May 26
, 2020 were enrolled if they had died or were discharged from ICU during the study period. Demographics, symptoms, vital signs, laboratory markers, supportive therapies, pharmacological treatments, medical and infectious complications were reported and compared between deceased and discharged patients.
A total of 663 patients were included. Overall ICU mortality was 31% (203 patients). At ICU admission non-survivors were more hypoxemic SpO
with non-rebreather mask, 90 (IQR 83 to 93) vs. 91 (IQR 87 to 94); P<.001 and with higher sequential organ failure assessment score SOFA, 7 (IQR 5 to 9) vs. 4 (IQR 3 to 7); P<.001. Complications were more frequent in non-survivors: acute respiratory distress syndrome (ARDS) (95% vs. 89%; P=.009), acute kidney injury (AKI) (58% vs. 24%; P<10
), shock (42% vs. 14%; P<10
), and arrhythmias (24% vs. 11%; P<10
). Respiratory super-infection, bloodstream infection and septic shock were higher in non-survivors (33% vs. 25%; P=.03, 33% vs. 23%; P=.01 and 15% vs. 3%, P=10
), respectively. The multivariable regression model showed that age was associated with mortality, with every year increasing risk-of-death by 1% (95%CI: 1 to 10, P=.014). Each 5-point increase in APACHE II independently predicted mortality OR: 1.508 (1.081, 2.104), P=.015. Patients with AKI OR: 2.468 (1.628, 3.741), P<10
), cardiac arrest OR: 11.099 (3.389, 36.353), P=.0001, and septic shock OR: 3.224 (1.486, 6.994), P=.002 had an increased risk-of-death.
Older COVID-19 patients with higher APACHE II scores on admission, those who developed AKI grades ii or iii and/or septic shock during ICU stay had an increased risk-of-death. ICU mortality was 31%.
Friction stir lap welds in AA 7075-T6 aluminium alloy were produced using tools with and without geometrical imperfections and varying welding pitch. Geometrical imperfections, resulting from the ...damage of the tool during the welding of the hard aluminium alloy, were simulated by machining small flats in the pin threads. Material adhesion to the worn tool was simulated by increasing the welding pitch. The welds produced were characterised, in the as-welded and heat-treated conditions, by performing monotonic and cyclic tensile-shear tests, micro-hardness measurements and metallography. The peak temperatures reached during welding were calculated using the spindle torque. No important differences in heat generation were registered when varying the welding conditions. The morphology and size of the lap weld defects were analysed in order to assess the influence of tool damage on welds properties. Material adhesion to the tool, simulated by increasing the welding pitch, showed to have a stronger influence on defect size than the thread imperfections. The small changes in welds defect size had no important effect on the monotonic strength of the welds, but had important influence on the fatigue behaviour. An increase of around 10% in the effective sheet thickness of the CL joints resulted in an increase of 500% in the fatigue life. Improved fatigue performance was also registered for the welds performed with the tool with pin imperfections indicating that sensitive tool damage will have no negative influence on the performance of the lap welds.
Amphibians are the most threatened group of vertebrates because they have certain biological and ecological characteristics that make them sensitive to environmental changes. The aim of this study ...was to evaluate the health status of field-collected adult frogs of Leptodactylus luctator (Amphibia, Anura) living in sites with different anthropogenic disturbances (florihorticulture, petrochemical industry and sewage discharges) and a reference site without any detectable influence of such activities. To this end, a battery of 21 biomarkers (hematological, biochemical and individual biomarkers) was studied using a multivariate approach that allows us to evaluate the relationship between them and provide information on their usefulness. The frogs at the florihorticulture, petrochemical and sewage discharges sites exhibited several biomarkers far from homeostasis. In addition, we identified 11 of 21 biomarkers that were useful indicators of the health status of the frogs and allowed discrimination between study sites in the following order: lymphocytes (98 %), neutrophils (45 %), hemoglobin (42 %), monocytes (41 %), fat body index (35 %), eosinophils (35 %), hepatosomatic index (33 %), mean corpuscular hemoglobin (32 %), thrombocytes (27 %), catalase in liver (26 %), and GST in liver (26 %). The results suggest that hematological biomarkers contribute the most to site separation, whereas biochemical biomarkers contribute the least. The integral interpretation of the results also allowed us to diagnose the different health status of L. luctator: The frogs from the petrochemical industry were the most negatively affected, followed by the frogs from the sewages discharges and finally the frogs from the florihorticulture and reference sites. This is the first field study with anurans in which so many biomarkers were examined.
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•Integral analysis of 21 biomarkers allowed diagnosing diverse frog health statuses.•Frogs in disturbed sites showed biomarkers far from homeostasis.•We identified 11 biomarkers indicative of frog health that distinguished each site.•We selected 9 sensitive biomarkers that require non-invasive methods.
COVID-19 induces coagulopathy associated with an increase of thromboembolic events. Due to the lack of agreement on recommendations for thromboprophylactic management, the aim of this study was to ...study the dosages of LMWH used in critically ill COVID-19 patients assessing the effect on their outcome.
We evaluated data of the Reg-COVID19. According to LMWH dose two groups were analyzed: prophylaxis and treatment. Primary outcome was the relationship of LMWH dosage with mortality. Secondary outcomes included the incidence of thrombotic and bleeding events, length of ICU stay, invasive mechanical ventilation, and thrombotic and inflammatory parameters.
Data of 720 patients were analyzed, 258 in the prophylaxis group and 462 in the treatment group. C Reactive Protein, invasive mechanical ventilation, tocilizumab and corticosteroid treatments were related with the choice of LMWH dose. Hemorrhagic events (66/720, 9.2%) and thrombotic complications (69/720, 9.6%) were similar in both groups (p = .819 and p = .265), as was the time course of the thrombotic events, earlier than hemorrhagic ones (9 3–18 and 12 6–19 days respectively). Mortality was lower in prophylaxis group (25.2% versus 35.1%), but once an inverse probability weighting model was applied, we found no effect of LMWH dose.
We found no benefit or harm with the administration of therapeutic or prophylactic LMWH dose in COVID19 critically ill patients. With a similar rate of hemorrhagic or thrombotic events, the LMWH dose had no influence on mortality. More studies are needed to determine the optimal thromboprophylaxis protocol for critically ill patients.
Los pacientes COVID-19 presentan una coagulopatía caracterizada por una elevada incidencia de complicaciones tromboembólicas. Ante la controversia existente sobre el manejo de la tromboprofilaxis, se llevó a cabo un estudio con el objetivo de analizar el efecto de las diferentes dosis de heparina de bajo peso molecular (HBPM) utilizadas en los pacientes críticos con COVID-19.
Se evaluaron datos del Reg-COVID19. Se compararon dos grupos de pacientes según la dosis de HBPM administrada: profilaxis y tratamiento. El objetivo primario fue determinar si había relación de la dosis de HBPM con la mortalidad. Los objetivos secundarios incluyeron la incidencia de eventos trombóticos y hemorrágicos, la duración de la estancia en UCI, la ventilación mecánica invasiva y parámetros trombóticos e inflamatorios.
Se analizaron datos de 720 pacientes, 258 en el grupo de profilaxis y 462 en el de tratamiento. La proteína C reactiva, la ventilación mecánica invasiva, y el tratamiento con tocilizumab o corticosteroides se relacionaron con la elección de la dosis de HBPM. La incidencia de complicaciones hemorrágicas (66/720, 9.2%) y trombóticas (69/720, 9.6%) fue similar en ambos grupos, al igual que el curso temporal de los eventos trombóticos, que ocurrieron antes que los hemorrágicos (9 3-18 y 12 6-19 días respectivamente). La mortalidad fue menor en el grupo de profilaxis (25.2% frente a 35.1%), pero al aplicar un modelo de ponderación de probabilidad inversa, no se encontraron diferencias entre los grupos.
No se encontraron efectos beneficiosos ni perjudiciales relacionados con la administración de dosis profilácticas o terapéuticas de HBPM en pacientes críticos COVID-19, con una tasa similar de complicaciones hemorrágicas o trombóticas. A partir de estos resultados, consideramos que son necesarios más estudios para determinar el protocolo óptimo de tromboprofilaxis en estos pacientes.
A simple method is presented for estimating the resonant frequency of compact slotted microstrip antennas, based on their current distribution. The method has been first tested in two basic and ...symmetric geometries; afterwards, through the combination of these geometries, a multi-slotted structure has been analysed. Prototypes have also been manufactured in RT/Duroid 6002 and FR4 substrates, and good agreement has been obtained between estimations, simulations and measurements. A maximum estimation error of 10% has been achieved with this method, providing a useful tool for the design of compact slotted microstrip antennas.
The use of a multipass welding strategy for increasing the bonding area in the dissimilar friction stir lap welding (FSLW) of aluminium to steel is analysed in current work. In order to minimize tool ...wear, the pin penetration into the lower plate, the steel plate, was set to a minimum. By performing partially overlapped welding passes it was possible to analyse the quality of the bonding across the multipass weld. The microstructural analysis of the bonding interface, after weld collapse in tensile-shear testing, enabled to conclude that by minimizing the pin penetration in the steel plate, the formation of intermetallics in the bonding interface is supressed and base materials joining results from mechanical bonding and solid state solution. However, for each welding pass, the bonding is not uniform/continuous across the pin trajectory. The deleterious effect of the bonding discontinuities on the monotonic weld strength may be limited by overlapping the successive weld passes, in order to maximize the bonding area. Improving the fatigue strength requires optimizing the welding parameters and/or pin positioning relative to the lower plate in order to avoid the occurrence of micro-cavities at the bonding interface.
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•Multipass friction stir lap welding of aluminium to steel•Mechanical bonding by a wavy interface and diffusion/solid solution•Interfacial failure in monotonic tensile-shear loading•Small discontinuities work as fatigue crack nucleation sites
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