Using biocontrol agents and sodium nitrophenolate to control powdery mildew and improve the growth and productivity of marigold (Calendula officinalis L.)

In vitro and in vivo studies were conducted to investigate the potential of four biocontrol agents (BCAs), namely Bacillus megaterium, Pseudomonas fluorescens, Trichoderma viride, and T. harzianum, individually and in combination with sodium nitrophenolate (SN) to control marigold powdery mildew. The results showed that all treatments led to a significant inhibition in the conidial germination of Golovinomyces cichoracearum in vitro. Maximum inhibition was recorded by T. harzianum (1×109 CFU mL-1) + SN (1.5%), followed by T. viride + SN, and B. megaterium + SN at the same concentrations as follows: 83.6, 79.1, and 70.6%, respectively. While the lowest inhibition (20.4%) was recorded by P. fluorescens (1×105 CFU mL-1). In the greenhouse, all treatments applied significantly reduced the disease severity and the area under the disease progress curve (AUDPC). The combination treatments had a better disease control response than individual treatments. Similar results were achieved in the field, where disease severity reduced to 9.2 and 10.3% in plants treated with T. harzianum + SN in the first and second seasons, respectively, compared to 40.2 and 44.1% in control in both seasons. Likewise, AUDPC reduced to 274 and 315 in plants treated with T. harzianum + SN in the first and second seasons, respectively, compared to 1207 and 1340 in control in both seasons. The treatments improved growth and productivity characteristics, as well as photosynthetic pigments, total phenolic compounds (TPC), and polyphenol oxidase (PPO) activity, while significantly reducing free proline (FP). In conclusion, BCAs applied individually or in combination with SN can be used effectively to suppress powdery mildew of marigold

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Manufacturing, mechanical properties and corrosion behaviour of high-Mn TWIP steels

Abstract Austenitic high-Mn (15–30 wt.%) based twinning-induced plasticity (TWIP) steels provide great potential in applications for structural components in the automotive industry, owing to their excellent tensile strength-ductility property combination. In certain cases, these steels might also substitute austenitic Cr-Ni stainless steels. The aim of this present work is to investigate the high-temperature flow resistance, recrystallisation and the evolution of microstructure of high-Mn steels by compression testing on a Gleeble simulator. The influence of Al alloying (0–8 wt.%) in the hot rolling temperature range (800°C–1100°C) is studied in particular, but also some observations are made regarding the influence of Cr alloying. Microstructures are examined in optical and electron microscopes. The results are compared with corresponding properties of carbon and austenitic stainless steels. In addition, the mechanical properties are studied briefly, using tension tests over the temperature range from -80°C to 200°C. Finally, a preliminary study is conducted on the corrosion behaviour of TWIP steels in two media, using the potentiodynamic polarization technique. The results show that the flow stress level of high-Mn TWIP steels is considerably higher than that of low-carbon steels and depends on the Al concentration up to 6 wt.%, while the structure is fully austenitic at hot rolling temperatures. At higher Al contents, the flow stress level is reduced, due to the presence of ferrite. The static recrystallisation kinetics is slower compared to that of carbon steels, but it is faster than is typical of Nb-microalloyed or austenitic stainless steels. The high Mn content is one reason for high flow stress as well as for slow softening. Al plays a minor role only; but in the case of austenitic-ferritic structure, the softening of the ferrite phase occurs very rapidly, contributing to overall faster softening. The high Mn content also retards considerably the onset of dynamic recrystallisation, but the influence of Al is minor. Similarly, the contribution of Cr to the hot deformation resistance and static and dynamic recrystallisation, is insignificant. The grain size effectively becomes refined by the dynamic and static recrystallisation processes. The tensile testing of TWIP steels revealed that the Al alloying and temperature have drastic effects on the yield strength, tensile strength and elongation. The higher Al raises the yield strength because of the solid solution strengthening. However, Al tends to increase the stacking fault energy that affects strongly the deformation mechanism. In small concentrations, Al suppresses martensite formation and enhances deformation twinning, leading to high tensile strength and good ductility. However, with an increasing temperature, SFE increases, and consequently, the density of deformation twins decreases and mechanical properties are impaired. Corrosion testing indicated that Al alloying improves the corrosion resistance of high-Mn TWIP steels. The addition of Cr is a further benefit for the passivation of these steels. The passive film that formed on 8wt.% Al-6wt.%Cr steel was found to be even more stable than that on Type 304 steel in 5–50% HNO3 solutions. A prolonged pre-treatment of the steel in the anodic passive regime created a thick, protective and stable passive film that enhanced the corrosion resistance also in 3.5% NaCl solution

Investigation of microstructure and mechanical properties of laser welded complex phase steel lap joints

Abstract In this study the microstructure and mechanical properties of laser welded complex phase steel lap joints were evaluated. Three different welding parameters were used in the experiments. The weld geometry and microstructure of the weld were studied. The joints were evaluated by hardness measurements, shear strength and fatigue strength tests. The geometry of the lap joints was affected by the welding parameters, and the width of the joint increased the lower the welding speed was. The weld metal (WM) microstructure with highest welding speed exhibits a fine columnar grain structure. As welding speed increased, the dendritic grain structure was coarser. With lowest welding speed, the microstructure changed to an equiaxed grain structure due to slower cooling. The WM with highest welding speed had the highest hardness with an average value 413 HV. The shear strengths of the joints were markedly influenced by the welding speed. With the lowest welding speed, the shear strength of the single weld was 222% higher than that of the highest welding speed. A joint with multiple welds achieved shear strength corresponding to the strength of the base material (1000 MPa). Fatigue limit of the lap joint with lowest welding speed was low < 20 MPa

Tehokkaat rakenteet:laserhitsattujen liitosten ominaisuudet

Tiivistelmä Tehokkaat rakenteet (TeRa) -hankkeessa pyrittiin edistämään yhteiskunnan vähähiilisyyden vaatimuksia rakenteiden materiaali-, energia- ja päästötehokkuuden kautta. Tehokkaiden rakenteiden suunnittelun ja valmistuksen kehittäminen johtaa kustannustehokkaampiin tuotteisiin, mikä mahdollistaa kilpailukykyiset valmistuskustannukset vähäisellä hiilijalanjäljellä. Hankkeessa kehitettiin teknisesti ja taloudellisesti tehokkaiden rakenteiden suunnittelu- ja valmistusmenetelmiä. Tehokkaat rakenteet hankkeen lähtökohtana oli Pohjois-Pohjanmaan älykkään erikoitumisen strategia ja hankkeen tukirankana oli vankka erikoisteräs-osaaminen sekä teräs- ja suunnitteluosaaminen uusien materiaalien hyödyntämisessä ja rakenteiden keventämisessä. Laserhitsausta hyödyntäen ultralujista teräksistä voidaan valmistaa entistä keveämpiä ja kestävämpiä rakenteita. Menetelmän etuna on pieni, tarkkaan kohdistettu lämmöntuonti sekä hitsausnopeus. Hankkeessa kehitettiin teknisesti ja taloudellisesti tehokkaiden rakenteiden suunnittelu- ja valmistusmenetelmiä. Ultralujille koemateriaaleille löydettiin entistä kustannustehokkaammat ja kestävyyden kannalta paremmat laserhitsauksen liitostavat. Laserhitsiliitosten, vähentyneen materiaalin tarpeen ja lujemman akenteen avulla ympäristövaikutukset pienenevät tuotteen koko elinkaaren aikana. Lopputuloksena hankkeessa valmistettiin teknisesti erinomaisia ja kustannustehokkaita rakenteita. Ultralujista teräksistä valmistettujen kennorakenteiden lujuusominaisuuksia tutkittiin erilaisten kokeiden avulla. Hankkeen tuloksena saatiin myös huomattavan paljon uutta tietoa ultralujien terästen laserhitsausliitoksista. Hankkeessa tehtiin merkittävä määrä laserhitsattujen limiliitosten ominaisuuksien tutkimiseen liittyviä kokeita. Hitsiliitoksia tutkittiin pääasiassa veto- ja väsytyskokeilla sekä liitosten mikrorakenne tutkimuksilla. Hankkeessa tehdyn kirjallisuustutkimuksen mukaan hankkeessa tutkitun AR600 ultralujan kulutusteräksen laserhitsausliitoksista ei löytynyt lainkaan aikaisemmin tutkittua tietoa, joten hankkeessa tehtyä tutkimusta voidaan pitää merkittävänä avauksena kyseisen materiaalin tutkimuksessa. Raportti perustuu Tehokkaat rakenteet (TeRa) -hankkeessa tehtyyn tutkimukseen. Tässä raportissa keskitytään pääasiassa laserhitsausliitosten koetulosten esittelyyn. TeRa-hanke on Euroopan aluekehitysrahaston EAKR-hanke ja sen on myöntänyt Pohjois- Pohjanmaan liitto. Hankkeen kuntarahoittajina ovat toimineet Nivala-Haapajärven seutukunta NIHAK r.y., Nivalan Teollisuuskylä Oy ja Nivalan kaupunki. Hankkeen yksityisrahoittajina ovat olleet Wärtsilä Finland Oy, SSAB Europe Oy, HT Laser Oy, Randax Oy, Konestar Oy ja Miilux Oy.Abstract The Efficient Structures (TeRa) project promoted society’s low-carbon requirements through the material, energy and emission efficiency of structures. Developing the design methods and manufacture of the structures will lead to more cost-effective products, enabling competitive manufacturing costs with a low carbon footprint. Methods for designing were developed in the project and manufacturing technically and economically efficient structures. The Efficient Structures project was based on Oulu Region’s smart specialization strategy. The project was also supported by special steel expertise as well as steel and design expertise in utilizing new materials and lightening structures. Based on the research carried out in the project, it became clear that by utilizing laser welding and ultra-high-strength steels even lighter and more durable structures can be manufactured. The advantage of the laser welding is the small heat input and the high welding speed. For ultra-high-strength steel test materials, more cost-effective and robust laser welded joints were developed. Laser welded joints, reduced need of material and a stronger structure reduce the environmental impact throughout the product’s life cycle. As a result, technically excellent and cost-effective structures were produced in the project. New types of structures were developed in the project. Benefits of different sandwich structures were demonstrated in the project. The strength properties of sandwich structures made of ultra-high-strength steels were studied by various experiments. The project carried out a significant number of experiments related to the study of the properties of laser welded lap joints. Laser welded joints were mainly studied by tensile and fatigue tests and by microstructure studies of joints. According to a literature review made in the project, no previously published papers were found on the laser welded joints of AR600 ultra-high-strength abrasion resistant steel studied in the project, so the research conducted in the project can be considered a significant opening in the study of that material. The project produced a significant number of peer-reviewed publications, demonstrating the internationally significant quality of the research carried out in the project. This report is based on research conducted in the Efficient Structures (TeRa) project. The report presents only some of the results of the project and this report focuses mainly on the test results of laser welded joints. The TeRa project is a European Regional Development Fund (ERDF) project and has been funded by the Council of Oulu Region. The Nivala-Haapajärvi region, NIHAK r.y., Nivalan Teollisuuskylä Oy and the city of Nivala have acted as municipal funders for the project. The private funders of the project have been Wärtsilä Finland Oy, SSAB Europe Oy, HT Laser Oy, Randax Oy, Konestar Oy and Miilux Oy

Enhancement of grain structure and mechanical properties of a high-Mn twinning-induced plasticity steel bearing Al–Si by fast-heating annealing

Abstract In this study, a cold-rolled Fe-0.01C-21.3Mn–3Al–3Si (wt.%) TWIP steel was undergone a fast-heating (FH) annealing at high temperatures of 1000–1200 °C and 2 s soaking time for grain refinement and controlling the phase structure and thereby to enhance the mechanical properties. For comparison, recrystallization annealing was conducted at lower temperatures of 650 and 700 °C for 180 s. The microstructural evolution of the FH annealed steel was surveyed using electron backscatter diffraction. The strain hardening behavior of the FH structures was studied by tensile tests. The tensile flow curves were also predicted by a phenomenological model based on the evolution of dislocation density during deformation. Fine mainly austenitic structure was promoted by FH annealing at 1000 and 1100 °C. At the lower temperatures of 650 and 700 °C, bands of finer grains, indicative of some inhomogeneity, were evident in the mostly austenitic recrystallized microstructure. However, at 1200 °C, the structure consisted of coarse austenite and ferrite with almost equal fractions. The FH annealed structures exhibited a remarkable improvement in the mechanical properties (a better combination of yield and tensile strength and ductility) compared to conventional long annealing cycles

Enhancement and underlying fatigue mechanisms of laser powder bed fusion additive-manufactured 316L stainless steel

Abstract In this study, the enhancement of additively manufactured (AM) 316L, by annealing, to the fully reversed tension-compression fatigue performance, in terms of fatigue life and fatigue damage, were investigated under two conditions: as-built (AB) and heat-treated (HT) at 900 °C. The underlying fatigue mechanisms were comprehensively characterised through intensive microstructural observations of cyclic-strained microstructures and fracture surfaces using laser confocal scanning microscopy (LCSM) and secondary electron imaging using scanning electron microscopy (SEM). The experimental results showed that the fatigue resistance of HT 316L was significantly enhanced by 100% as the fatigue limit was increased from 75 to 150 MPa for AB and HT 316L, respectively. The fatigue cracking mechanism in AB 316L is mainly related to two imperfections of the AM-induced microstructural components: residual stresses, which cause highly localised deformation, and dendritic cellular structures, which possess a weak link in their grain boundaries against crack propagation. Upon heat treatment at 900 °C, the residual stresses and dendritic structure were effectively reduced. Consequently, the fatigue life of AM 316L was significantly enhanced by promoting the formation of high-angle boundaries. More precisely, the cyclic deformation processes in fatigued HT 316L involve persistent slip bands and strain hardening

Grain size affecting the deformation characteristics via micro-injection upsetting

Abstract The micro-injection upsetting (MIU) experiments of commercially pure aluminium have been conducted on two groups of specimens with different grain structures. One group is of coarse grain (CG, undeformed) and the other group is of fine grain (FG) achieved via the 4th pass equal channel angular pressing in micro-meso/scale. The two groups were further processed by micro/meso-scale extrusion before conducting MIU for fabricating tiny pins. Micro-upsetting test of the tiny pins showed that the material has a good isotropic flow forming and is free of undesirable defects comparing with the CG counterparts, which can be ascribed to the decreasing of grain boundary strengthening effect in the case of FG structure

A new processing route to develop nano-grained structure of a TRIP-aided austenitic stainless-steel using double reversion fast-heating annealing

Abstract A novel processing route comprising double reversion annealing (DRA) was designed for developing bulk nano-grained (NG) structure of an austenitic stainless steel (Type 301LN). The new processing concept of DRA comprised two subsequent intrinsic type processes i.e., two times cold reductions (∼53 % and 63 %) followed by fast induction heating (∼200 °C/s) and short duration annealing at different temperatures (first at 690 °C/60s and second at 750–900 °C/0.1–1s). The NG structure revealed a remarkable improvement of the mechanical properties compared to the counterparts processed by single reversion annealing. Furthermore, outstanding combination of strength and formability is achieved for the DRA structures, significantly higher than those of high-Mn TWIP steels, low-alloy TRIP steels and 304 stainless steel. For instance, a superior combination of yield strength (∼950–1030 MPa) and formability index (11.8–12.5 mm) obtained after DRA at 750 °C/0.1s and 800°C/1 s, respectively. However, the corresponding values are 300 MPa and 12 mm for TWIP steels, 500 MPa and 10 mm for TRIP steels, and 270 MPa and 12 mm for 304 stainless steel. In order to reveal the effect of DRA on the stretch formability, Erichsen cup testing was conducted of both the initial and DRA steel specimens. Moreover, Erichsen cup testing also simulated by the finite element method (FEM) to survey further details of their deformation