Designing for Shape Memory in Additive Manufacturing of Cu–Al–Ni Shape Memory Alloy Processed by Laser Powder Bed Fusion

Shape memory alloys (SMAs) are functional materials that are being applied in practically all industries, from aerospace to biomedical sectors, and at present the scientific and technologic communities are looking to gain the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMAs, constitutes a real challenge due to the particularly well controlled microstructure required to exhibit the functional property of shape memory. In the present work, the design of the complete AM processing route, from powder atomization to laser powder bed fusion for AM and hot isostatic pressing (HIP), is approached for Cu–Al–Ni SMAs. The microstructure of the different processing states is characterized in relationship with the processing parameters. The thermal martensitic transformation, responsible for the functional properties, is analyzed in a comparative way for each one of the different processed samples. The present results demonstrate that a final post–processing thermal treatment to control the microstructure is crucial to obtain the expected functional properties. Finally, it is demonstrated that using the designed processing route of laser powder bed fusion followed by a post–processing HIP and a final specific thermal treatment, a satisfactory shape memory behavior can be obtained in Cu–Al–Ni SMAs, paving the road for further applications.This research was supported by the Industry Department of the Basque Government through the ELKARTEK–CEMAP (KK–2020/00047) project, as well as from the GIU–17/071 from the University of the Basque Country UPV/EHU. Financial support was also received from the Spanish Ministry of Economy and Competitiveness, MINECO, through the project MAT2017-84069P. This work made use of the facilities from the Electronic Microscopy and Material Microanalysis Service of the SGIKER from the UPV/EHU. M.P.-C. acknowledges the pre–doctoral grant (PRE_2019_2_0268) from the Education Department of the Basque Country. J.F.G.-C. thanks the post–doctoral grant (ESPDOC18/37) from the UPV/EHU

Field-dependent roughness of moving domain walls in a Pt/Co/Pt magnetic thin film

The creep motion of domain walls driven by external fields in magnetic thin films is described by universal features related to the underlying depinning transition. One key parameter in this description is the roughness exponent characterizing the growth of fluctuations of the domain wall position with its longitudinal length scale. The roughness amplitude, which gives information about the scale of fluctuations, however, has received less attention. Albeit their relevance, experimental reports of the roughness parameters, both exponent and amplitude, are scarce. We report here experimental values of the roughness parameters for different magnetic field intensities in the creep regime at room temperature for a Pt/Co/Pt thin film. The mean value of the roughness exponent is $\zeta = 0.74$, and we show that it can be rationalized as an effective value in terms of the known universal values corresponding to the depinning and thermal cases. In addition, it is shown that the roughness amplitude presents a significant increase with decreasing field. These results contribute to the description of domain wall motion in disordered thin magnetic systems.Comment: 10 pages, 7 figure

Internal friction associated with ε martensite in shape memory steels produced by casting route and through additive manufacturing: Influence of thermal cycling on the martensitic transformation

Among the different families of shape memory alloys (SMA), the Fe-Mn-Si-Cr-Ni alloys have attracted a renewed interest because of its low cost, high corrosion resistance and high recovery strength during the shape memory effect, and the new technologies of additive manufacturing offer unforeseen possibilities for this family of SMA. In the present work, the reversible gamma - epsilon martensitic transformation (MT), responsible for the shape memory effect, is studied in two Fe-Mn-Si-Cr-Ni alloys with high (20.2 wt%) and low (15.8 wt%) Mn content, produced by the conventional route of casting and rolling, in comparison with the MT in another similar alloy, with intermediate Mn content (19.4 wt%), which was produced by gas atomization and additive manufacturing through laser metal deposition. The forward and reverse gamma - epsilon MT is studied by mechanical spectroscopy through the internal friction spectra and the dynamic modulus variation, together with a parallel microstructural characterization including in-situ observation of the gamma - epsilon MT during cooling and heating at the scanning electron microscope. The evolution of the transformed fraction of epsilon martensite, evaluated through the integral area of the internal friction peak, was followed along thermal cycling in all three alloys. Both, the internal friction and the electron microscopy studies show that the epsilon martensite amount increases very fast during the first few cycles, and then decreases with a tendency towards its stabilization for many tens of cycles. The results show that the gamma - epsilon MT is more stable on cycling in the additive manufactured sample than in the conventionally processed samples, opening new avenues for designing shape memory steels to be specifically processed through additive manufacturing.This work was supported by the ELKARTEK-CEMAP (KK-2020/00047) project from the Industry Department of the Basque Government, and the GIU-17/071 from the University of the Basque Country, UPV/EHU. This work made use of the SGIKER facilities at the UPV/EHU

Impact of growth conditions on the domain nucleation and domain wall propagation in Pt/Co/Pt stacks

Understanding the effect of fabrication conditions on domain wall (DW) motion in thin films with perpendicular magnetization is a mandatory issue in order to tune their properties aiming to design spintronics devices based on such phenomenon. In this context, the present work intends to show how different growth conditions may affect DW motion in the prototypical system Pt/Co/Pt. The trilayers were deposited by dc sputtering, and the parameters varied in this study were the Co thickness, the substrate roughness and the base pressure in the deposition chamber. Magneto-optical Kerr effect-based magnetometry and microscopy combined with x-ray reflectometry, atomic force microscopy and transmission electron microscopy were adopted as experimental techniques. This permitted us to elucidate the impact on the hysteresis loops and on the DW dynamics, produced by different growth conditions. As other authors, we found that Co thickness is strongly determinant for both the coercive field and the DW velocity. On the contrary, the topographic roughness of the substrate and the base pressure of the deposition chamber evidence a selective impact on the nucleation of magnetic domains and on DW propagation, respectively, providing a tool to tune these properties. </p

Clinical and Non-Clinical Variables Associated With Preventive and Curative Dental Service Utilisation: A Cross-Sectional Study Among Adolescents and Young Adults in Central Mexico

Objective The present study aimed to identify preventive and curative dental health service utilisation (DHSU) in the context of associated clinical and non-clinical factors among adolescents and young adults in Mexico. Design Cross-sectional study. Setting Applicants to a public university in Mexico. Participants Participants were 638 adolescents and young adults aged 16–25 randomly selected from university applicants. Interventions Data were collected using a self-administered questionnaire filled out by the students. For assessment of dental caries experience, we used the index of decayed, missing and filled teeth. Primary outcome The dependent variable was DHSU in the previous 12 months, coded as 0=non-use, 1=use of curative services and 2=use of preventive services. Results The mean age was 18.76±1.76 years, and 49.2% were women. The prevalence of DHSU was 40.9% (95% CI 37.1 to 44.8) for curative services and 22.9% (95% CI 19.7 to 26.3) for preventive services. The variables associated with curative services were age, sex, mother’s education, dental pain in the previous 12 months, caries experience, use of self-care devices and oral health knowledge. For preventive services, the variables associated were mother’s education, dental pain in the previous 12 months, caries experience, use of self-care devices and self-perception of oral health. Conclusions While differences emerged by type of service, a number of variables (sociodemographic and socioeconomic characteristics as well as dental factors) remained in the final model. Greater oral health needs and socioeconomic inequalities remained as predictors of both types of DHSU. Given the differences revealed by our study, oral health policies should refer those seeking dental care for oral diseases to preventive services, and promote the use of such services among the poorer and less educated population groups

Designing for shape memory in additive manufacturing of Cu-Al-Ni shape memory alloy processed by laser powder bed fusion

Shape memory alloys (SMAs) are functional materials that are being applied in practically all industries, from aerospace to biomedical sectors, and at present the scientific and technologic communities are looking to gain the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMAs, constitutes a real challenge due to the particularly well controlled microstructure required to exhibit the functional property of shape memory. In the present work, the design of the complete AM processing route, from powder atomization to laser powder bed fusion for AM and hot isostatic pressing (HIP), is approached for Cu-Al-Ni SMAs. The microstructure of the different processing states is characterized in relationship with the processing parameters. The thermal martensitic transformation, responsible for the functional properties, is analyzed in a comparative way for each one of the different processed samples. The present results demonstrate that a final post-processing thermal treatment to control the microstructure is crucial to obtain the expected functional properties. Finally, it is demonstrated that using the designed processing route of laser powder bed fusion followed by a post-processing HIP and a final specific thermal treatment, a satisfactory shape memory behavior can be obtained in Cu-Al-Ni SMAs, paving the road for further applications

PAISAJES DE ESPAÑA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Blood culture-negative infective endocarditis: a worse outcome? Results from a large multicentre retrospective Spanish cohort study

[Background] To assess the impact of blood cultures negative infective endocarditis (BCNIE) on in-hospital mortality.[Methods] Prospective multicentre study with retrospective analysis of a Spanish cohort including adult patients with definite IE. Cardiac implantable devices infection were excluded. Comparisons between blood cultures positive and BCNIE groups were performed to analyse in-hospital mortality.[Results] 1001 cases were included of which 83 (8.3%) had BCNIE. Alternative microbiological diagnosis was achieved for 39 (47%) out 83 cases. The most frequent identifications were: Coxiella burnetii (11; 28.2%), Tropheryma whipplei (4; 10.3%), Streptococcus gallolyticus (4;10.3%) and Staphylococcus epidermidis (3; 7.7%). Surgery was performed more frequently in BCNIE group (57.8 vs. 36.9%, p < .001). All-cause in-hospital mortality rate was 26.7% without statistical difference between compared groups. BCNIE was not associated to worse mortality rate in Cox regression model (aHR = 1.37, 95% CI 0.90–2.07, p = .14). Absence of microbiological diagnosis was also not associated to worse in-hospital prognosis (aHR = 1.62, 95% CI 0.99–2.64, p = .06).[Conclusions] In our cohort, BCNIE was not associated to greater in-hospital mortality based in multivariate Cox regression models. The variables most frequently associated with mortality were indicated but not performed surgery (aHR = 2.48, 95% CI 1.73–3.56, p < .001), septic shock (aHR = 2.24, 95% CI 1.68–2.99, p < .001), age over 65 years (aHR = 1.88, 95% CI 1.40-2.52, p < .001) and complicated endocarditis (aHR = 1.79, 95% CI 1.36–2.37, p < .001).Peer reviewe

Evaluation of two treatment strategies for the prevention of preterm birth in women identified as at risk by ultrasound (PESAPRO Trial): Study protocol for a randomized controlled trial

Background: Premature birth is considered one of the main problems in modern Obstetrics. It causes more than 50 % of neonatal mortality; it is responsible for a large proportion of infant morbidity and incurs very high economic costs. Cervical length, which can be accurately measured by ultrasound, has an inverse relationship with the risk of preterm birth. As a result, having an effective intervention for asymptomatic patients with short cervix could reduce the prematurity. Although recently published data demonstrates the effectiveness of vaginal progesterone and cervical pessary, these treatments have never been compared to one another. Methods/Design: The PESAPRO study is a noncommercial, multicenter, open-label, randomized clinical trial (RCT) in pregnant women with a short cervix as identified by transvaginal ultrasonography at 19 to 22 weeks of gestation. Patients are randomized (1:1) to either daily vaginal progesterone or cervical pessary until the 37th week of gestation or delivery; whichever comes first. During the trial, women visit every 4 weeks for routine questions and tests. The primary outcome is the proportion of spontaneous preterm deliveries before 34 weeks of gestation. A sample size of 254 pregnant women will be included at 29 participating hospitals in order to demonstrate noninferiority of placing a pessary versus vaginal progesterone. The first patient was randomized in August 2012, and recruitment of study subjects will continue until the end of December 2015. Discussion: This trial assesses the comparative efficacy and safety between two accepted treatments, cervical pessary versus vaginal progesterone, and it will provide evidence in order to establish clinical recommendationsThe study has been funded by two national grants from the Spanish Ministry of Health and ISCIII

ECAMulticapa: Effectiveness of double-layered compression therapy for healing venous ulcers in primary care: a Study Protocol

Background: Chronic venous insufficiency, in its final stage can cause venous ulcers. Venous ulcers have a prevalence of 0.5 % to 0.8 % in the general population, and increases starting at 60 years of age. This condition often causes increased dependency in affected individuals, as well as a perceived reduced quality of life and family overload. Local Treating chronic venous ulcers has 2 components: topically healing the ulcer and controlling the venous insufficiency. There is evidence that compressive therapy favours the healing process of venous ulcers. The studies we have found suggest that the use of multilayer bandage systems is more effective than the use of bandages with a single component, these are mostly using in Spain. Multilayer compression bandages with 2 layers are equally effective in the healing process of chronic venous ulcers as 4-layer bandages and are better tolerated and preferenced by patients. More studies are needed to specifically compare the 2-layer bandages systems in the settings where these patients are usually treated. Method/design: Randomised, controlled, parallel, multicentre clinical trial, with 12 weeks of follow-up and blind evaluation of the response variable. The objective is to assess the efficacy of multilayer compression bandages (2 layers) compared with crepe bandages, based on the incidence of healed venous ulcers in individuals treated in primary care nursing consultations, at 12 weeks of follow-up. The study will include 216 individuals (108 per branch) with venous ulcers treated in primary care nursing consultations. The primary endpoint is complete healing at 12 weeks of follow-up. The secondary endpoints are the degree of healing (Resvech.2), quality of life (CCVUQ-e), adverse reactions related to the healing process. Prognosis and demographic variables are also recorder. Effectiveness analysis using Kaplan-Meier curves, a log-rank test and a Cox regression analysis. The analysis was performed by intention to treat. Discussion: The study results can contribute to improving the care and quality of life of patients with venous ulcers, decreasing healing times and healthcare expenditure and contributing to the consistent treatment of these lesions. Trial registration: This study has been recorded in the Clinical Trials.gov site with the code NCT02364921. 17 February 2015.This study was funded by PN of I + D + I 2013–2016 and the ISCIII – Subdirección General de Evaluación y Fomento de la Investigación and FEDER funds (PI13/01975). Ministerio de Economia y Competitividad