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•Twins are suppressed in the fusion zone.•There is no indication of heat affected zone for the medium or high entropy alloy welds in the annealed condition.•Finer elongated grains are ...formed in the fusion zone of the high entropy alloy than that of the medium entropy alloy.•A specific 〈100〉 fibre along the transversal direction and specific texture components are formed in the fusion zone of the high entropy alloy and medium alloy welds, respectively.
This work explores the feasibility of producing bead-on-plate welds of a CrCoNi medium entropy alloy and a CrMnFeCoNi high entropy alloy using electron beam welding. The alloys were welded in two states: one in an as-cold-rolled condition and the other in an annealed condition. In addition, the materials are welded with two different parameters. The FCC microstructure of the welds is investigated using scanning electron microscopy assisted by energy-dispersive X-ray spectroscopy and electron-backscattered diffraction. The impact of the weld on the microstructure is discussed. The heat-affected zone is negligible for the annealed condition of both medium and high entropy alloys since there is no driving force for recrystallisation and the exposure time to high temperature is insufficient for grain coarsening. The texture formed in the fusion zone is also discussed and compared to the texture in the base metal and the heat-affected zone. Although the grain growth along the 〈100〉 crystallographic direction is preferential in all cases, the crystallographic texture type differs from each weld. Higher hardness values are measured in the medium entropy alloy's base metal and fusion zone than in the high entropy alloy.
The new alloying concept of multi-element systems with defined entropy (HEA—high-entropy alloy; MEA—medium-entropy alloy) is gaining increasing importance in materials research. Significantly ...improved properties or combinations of properties are shown by some HEA/MEA systems. Thus, primarily the production and resulting microstructures of HEA, as well as its properties, have been investigated so far. Furthermore, processing is a main issue in transferring HEA systems from the laboratory to real components. Since welding is the most important joining process for metals, it is crucial to investigate the influence of welding to guarantee component integrity. Welding leads to residual stresses, which significantly affect the component integrity. Hence, the focus of this study is the residual stress formation and distribution in a CoCrFeMnNi HEA and ternary CoCrNi MEA using two different welding processes: tungsten inert gas (TIG) welding and solid-state friction stir welding (FSW). As a pathway for the application of HEA in this investigation, for the first time, residual stress analyses in realistic near-component specimens were performed. The residual stresses were determined by X-ray diffraction (XRD) on the surfaces of top and root weld side. The results were correlated with the local welding microstructures. The results show that both FSW and TIG generate significant tensile residual stresses on the weld surfaces in, and transverse to, the welding direction. In the case of FSW of the CoCrFeMnNi HEA, the longitudinal residual stresses are in the range of the yield strength of approx. 260 MPa in the weld zone.
Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and ...development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation.
In August 2007, October 2008 and September–October 2010, 241 Tucker trawl and plankton net tows were conducted at the surface to depths of 1377 m at six locations in the northern and eastern Gulf of ...Mexico (GOM) to document leptocephalus diversity and determine how assemblage structure, larval size, abundance and isotopic signatures differ across the region and with depth. Overall, 2696 leptocephali representing 59 distinct taxa from 10 families were collected. Five families accounted for 96% of the total catch with Congridae and Ophichthidae being the most abundant. The top four most abundant species composed 59% of the total catch and included: Ariosoma balearicum, Paraconger caudilimbatus, Rhynchoconger flavus and Ophichthus gomesii. Four anguilliform species not previously documented in the GOM as adults or leptocephali were collected in this study, including Monopenchelys acuta, Quassiremus ascensionis, Saurenchelys stylura and one leptocephalus only known from its larval stage, Leptocephalus proboscideus. Leptocephalus catches were significantly greater at night than during the day. Catches at night were concentrated in the upper 200 m of the water column and significantly declined with increasing depth. Leptocephali abundances and assemblages were significantly different between sites on the upper continental slope (c. 500 m depth) and sites on the middle to lower continental slope (c. 1500–2300 m). Sites on the lower continental slope had a mixture of deep‐sea demersal, bathypelagic and coastal species, whereas upper‐slope sites contained several numerically dominant species (e.g., A. balearicum, P. caudilimbatus) that probably spawn over the continental shelf and upper slope of the GOM. Standard lengths of the four dominant species differed between sites and years, indicating heterochronic reproduction and potential larval source pools within and outside of the GOM. Stable‐isotope analyses (δ13C and δ15N) conducted on 185 specimens from six families revealed that leptocephali had a wide range of isotopic values at the family and size‐class levels. Species in the families Muraenidae, Congridae and Ophichthidae had similar δ15N values compared with the broad range of δ15N values seen in the deep‐sea families Nemichthyidae, Nettastomatidae and Synaphobranchidae. Stable‐isotope values were variably related to length, with δ15N values being positively size correlated in ophichthids and δ13C values being negatively size correlated in A. balearicum and P. caudilimbatus. Results suggest that leptocephali feed in various water depths and masses, and on different components of POM, which could lead to niche partitioning. Ecological aspects of these important members of the plankton community provide insight into larval connectivity in the GOM as well as the early life history of Anguilliformes.
Introduction: As the world struggles to manage and move forward from the clinical effects of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the ability to test for viral genomic RNA in ...patient samples is critical. Currently, the development and performance of SARS-CoV-2 clinical tests is impaired by a diminished supply chain of reagents needed for the tests, compelling labs to seek alternative, readily-available reagents as substitutes. Aim: To evaluate the suitability of Phosphate-Buffered Saline (PBS) and RNAlater™ as substitutes for sample transport media, to preserve the fidelity of viral RNA for use in a SARS-CoV-2 RT-PCR assay. Materials and Methods: This molecular study was conducted in Dayton, Ohio (USA) using synthetic materials and de-identified remnant patient specimens. Simulated standard clinical laboratory storage conditions were used, including prolonged storage up to 72 hours at 2-8°C and a freeze/thaw cycle. PCR amplification performance was measured for PBS and RNAlater™ against transport medium as a reference using purified viral RNA. Performance differences were determined using repeated-measures two-way ANOVA with a 5% false discovery rate. Results: Results indicate that both solutions were suitable for testing viral RNA in the short term, but the viral RNA stored in PBS began to degrade after just 24 hours at 2-8°C. In contrast, RNAlater™ preserved the viral RNA out to 72 hours when stored at 2-8°C, with no statistically significant decrease in the detection limits compared to freshly-prepared viral RNA dilutions. A single freeze/thaw cycle raised the lower limit of detection for RNAlater™-preserved viral RNA slightly. Conclusion: The current (as of April 2020) CDC sample guidelines permit the use of PBS, but have not published data to support this claim. These results offer an alternative to the transport options outlined in many Emergency Use Authorisations (EUA) currently authorised for use in diagnostic testing and may be used for possible long-term storage solutions for studies investigating SARS-CoV-2.
First Blood, Apocalypse Now, The Deer Hunter, Platoon, Full Metal Jacket, Born on the Fourth of July, and Good Morning, Vietnam, along with many other likeminded films, convey a dark message of this ...conflict that overpower the victorious themes of more traditional "war movies" (John Wayne in The Green Berets, for example).2-4 From the vantage point of the present it is almost inconceivable to envisage a time when the war in Vietnam was apparently under control, appeared winnable, and military personnel, including doctors, were generally confident and hopeful. During her two tours in the South China Sea, about 23,000 patients had been admitted (over one-third of whom were WIA- wounded in action); the overwhelming majority survived and were either returned to full duty, or evacuated to landbased hospitals for further treatment in the Pacific region or the continental United States.10,11 In September 1967, Navy psychiatrists LCDR Robert E. Strange and CDR Ransom J. Arthur published a brief article reporting their psychiatric experience aboard the USS Repose during her first seven months of operations in Vietnam beginning in February 1966.12 This report was the first to describe the activities of a U.S. hospital ship in a combat zone since the Korean War. Arthur (1925-1989) graduated MD in 1951 from Harvard then practiced family medicine in Hawaii; later he undertook specialist training in psychiatry in both Honolulu and the US Naval Hospital in Bethesda and became a medical officer first at Oakland Naval Hospital then at the Navy Medical Neuropsychiatric Research Unit at San Diego where he eventually became Commanding Officer; he retired from the Navy in 1974.13,14 Strange and Arthur described the Repose's psychiatric quarters noting its 48-bed complement; that it was an "openunlocked unit" in which patients were allowed "freedom of movement about the ship commensurate with their degree of illness and responsibility" and that it was staffed by one physician, one psychiatric nurse, and nine hospital corpsmen. In July 1968, SKF which had a monopoly on Thorazine®, produced a marketing brochure for this product that was a facsimile reprint of the Strange and Arthur piece retitled as "A Report from Viet Nam-Hospital Ship Psychiatry in a War Zone" and with a front cover illustration of the USS Repose and back covers emblazoned with the SKF corporate logo and full prescribing information and technical details for Thorazine® described as a tranquilizer, potentiator, and antiemetic.28 This brochure also carried pull-quotes in large print in which the naval psychiatrists endorsed the drug (as was quoted above). Because the authors were in the employ of the U.S. Government, the work would be considered to be in the public domain, but copyright would have been held by the journal that originally published it so some form of agreement would have had to be arranged between all parties.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK, VSZLJ
To address this gap, Strange and Capt. Dudley E. Brown MC USN (Head, Neuropsychiatry branch, Bureau of Medicine and Surgery, Washington, DC) coauthored a study involving 100 Marine and Navy patients ...at the Naval Hospital to ascertain if returnees who had been in combat in Vietnam were likely to be more violent than servicemen who were noncombatants. Hostilities in Vietnam were still in their early stages, despite innumerable fire fights and dangerous missions; the years from 1968 on would see the intensity, scope, and human destructiveness of the war increase. ...although conscription was enacted, the more stringent requirements of the Navy and Marine Corps, which also was highly dependent on volunteers, likely resulted in service personnel who had a more developed esprit de corps and commitment to military service as a "career." ...as this was touted as the first war during which the pharmaceutical agent phenothiazine (Thorazine/chlorpromazine) was available and used and which the pharmaceutical company manufacturing it made much of, how widespread was the prescribing of such antipsychotics? ...a common theme in the history of medicine is the link between clinical innovations in wartime and their later beneficial transfer to civilian medicine: included are plastic and orthopedic surgical techniques; antibiotics; blood banking and transfusions; trauma care; and emergency first responders' technology and protocols.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Within the past two decades, several American bibliographies of comic art have been published to aid in research on comics and cartooning. Professor John Lent’s ten-volume Comic Art Bibliographies is ...one of the largest such projects and he began it with a self-published volume in 1986. Librarian Randy Scott published The Comic Art Collection Catalog: An Author, Artist, Title and Subject Catalog Of The Comic Art Collection, Special Collections Division, Michigan State University Libraries, whi...
For a significant increase in the strength of high-strength fine-grained structural steels with a nominal yield strength ≥690 MPa, the addition of microalloying elements such as Nb and Ti is ...required. The standard specifications for the chemical composition of these steels (e.g., in EN 10025-6) often only give the manufacturer limit contents to achieve the defined properties. The effect of the alloying elements in the heat affected zone (HAZ) is sometimes completely contrary. This makes it difficult to adequately predict the batch dependency regarding weldability and the load-bearing behaviour of the welded joint. Three different micro-alloyed steels of the grade S690QL were produced on a laboratory scale, focusing on different Nb and Ti contents. To investigate the tempering effect, these were gas metal arc welded in three layers. In addition to metallographic investigations of individual HAZ areas, thermodynamic phase calculations were carried out using Thermo-Calc, following variations in the chemical composition. This provides an understanding of phase transformation, precipitation growth, and dissolution during welding as a function of temperature and cooling conditions. The results show a divergent metallurgical behaviour in the HAZ of the three different micro-alloyed steels. Thereby, the Ti micro-alloyed grade showed a strong softening of the HAZ in contrast to the Nb micro-alloyed grade. This can be attributed to a contrary precipitation behaviour during welding.
Metals that are exposed to high pressure hydrogen gas may undergo detrimental failure by embrittlement. Understanding the mechanisms and driving forces of hydrogen absorption on the surface of metals ...is crucial for avoiding hydrogen embrittlement. In this study, the effect of stress-enhanced gaseous hydrogen uptake in bulk metals is investigated in detail. For that purpose, a generalized form of Sievert's law is derived from thermodynamic potentials considering the effect of microstructural trapping sites and multiaxial stresses. This new equation is parametrized and verified using experimental data for carbon steels, which were charged under gaseous hydrogen atmosphere at pressures up to 1000 bar. The role of microstructural trapping sites on the parameter identification is critically discussed. Finally, the parametrized equation is applied to calculate the stress-enhanced hydrogen solubility of thin-walled pipelines and thick-walled pressure vessels during service.
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•Improvement of Sievert's law to consider trapping sites and stress states.•Calculation and validation of gaseous hydrogen solubility under extreme conditions.•Hydrogen uptake measured for L450 steel at 200 and 1000 bar.•Calculation of the hydrogen solubility in pipes and pressure vessels.•Comprehensive literature survey of gaseous hydrogen solubility.
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