Microstructural Characteristics and Mechanical Properties of Low-Alloy, Medium-Carbon Steels After Multiple Tempering

The microstructure and mechanical properties of NiCrMoV- and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature, regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels

A comparison of microstructure and mechanical properties of low-alloy-medium-carbon steels after quench-hardening

The microstructural characteristics of three medium carbon steels, namely MnCrB, NiCrSi and NiCrMoV containing steels, have been investigated when the steels were hardened by quenching in water or oil from different austenitisation temperatures (i.e. 850, 900 and 950 °C). The microstructure was characterised using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, and X-Ray diffraction technique, whereas the mechanical properties were measured by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The microscopy observations suggested a fully martensitic microstructure, whereas martensite was considerably finer in NiCrSi and NiCrMoV steels compared to MnCrB steel. Moreover, the NiCrSi and NiCrMoV steels showed significantly higher strengths and lower ductility than MnCrB steel. The results suggested that the small additions of alloying elements and different prior austenite grain sizes were mainly responsible for the observed microstructural and mechanical properties variations

Case Study: Wear Mechanisms of NiCrVMo-steel and CrB-steel Scrap Shear Blades

Shear blades are extensively used in the recycling of metal scrap. A comparative study was conducted on used medium carbon NiCrVMo and CrB containing steel scrap shear blades to better understand their wear mechanisms under service conditions. The microstructure and hardness of worn cutting edges and bulk material were characterised by optical microscopy, scanning electron microscopy and microanalysis, X-ray diffraction analysis and macro/micro hardness testing. Moreover, tensile and Charpy impact properties were obtained from the bulk material. Several wear mechanisms were identified in both blades which are categorised in two main groups, i.e. spalling and progressive wear. The progressive wear due to abrasive, adhesive and oxidation wear was observed in both blades. In NiCrVMo-steel blades, spalling and crack propagation from surface/subsurface white etching layers mainly caused the severe wear. However, spalling due to delamination wear and crack propagation from severely subsurface deformed layers was the dominant severe wear mechanism in CrB-steel blades

Oil and Gas Impacts on Wyoming’s Sagegrouse: Summarizing the Past and Predicting the Foreseeable Future

Historical impacts from oil and gas development to greater sage-grouse (Centrocercus urophasianus) habitat are well-documented in some areas of Wyoming, in particular within natural gas development fields, such as the Powder River Basin and JonahPinedale. The drilling techniques and pad densities in these fields have been extrapolated to estimate future oil and gas impacts in the U. S. Fish and Wildlife Service (2010) warranted-but-precluded listing determination for the sage-grouse under the Endangered Species Act. Further, assumptions regarding the scale of oil and gas development are incorporated within various resource management plan amendments by the Bureau of Land Management (BLM) throughout the range of the sage-grouse. We evaluated the status of Wyoming sage-grouse leks by quantifying the scale of oil and gas impacts across the state of Wyoming and the extent that sage-grouse persistence is impacted by oil and gas development using the impact analysis lens of well-pad density within a 3.2-km radius of a lek (Doherty et al. 2010). The analysis provides that 75% (1,770 out of 2,356 leks analyzed) of identified leks (active and inactive) have(Doherty et al. 2010). As to future development of oil and gas in Wyoming, 64% of Wyoming leks (1,508 leks) are protected from oil and gas development densities of \u3e12 wells per 32.2-km2 , due to prescriptive density and disturbance restrictions within the Wyoming Core Area Policy. The Wyoming Core Area Policy protects priority sage-grouse habitats by limiting surface disturbance to an average of 5%. Specific to oil and gas development, a prescriptive density standard allows an average of 1 well pad per square mile. Thus, the combination of core area protections with the technological shift to directional and horizontal drilling that is being deployed in both existing and new fields to recover hydrocarbons (i.e., technologies that dramatically reduce the fragmentation and disturbance profiles of oil and gas development), suggests that threat projections in the U.S. Fish and Wildlife Service (2010) listing decision on sage-grouse due to future oil and gas development have been overstated

The impact of exchanging the light and heavy chains on the structures of bovine ultralong antibodies

The third complementary‐determining regions of the heavy‐chain (CDR3H) variable regions (VH) of some cattle antibodies are highly extended, consisting of 48 or more residues. These `ultralong' CDR3Hs form β‐ribbon stalks that protrude from the surface of the antibody with a disulfide cross‐linked knob region at their apex that dominates antigen interactions over the other CDR loops. The structure of the Fab fragment of a naturally paired bovine ultralong antibody (D08), identified by single B‐cell sequencing, has been determined to 1.6 Å resolution. By swapping the D08 native light chain with that of an unrelated antigen‐unknown ultralong antibody, it is shown that interactions between the CDR3s of the variable domains potentially affect the fine positioning of the ultralong CDR3H; however, comparison with other crystallographic structures shows that crystalline packing is also a major contributor. It is concluded that, on balance, the exact positioning of ultralong CDR3H loops is most likely to be due to the constraints of crystal packing

Correction: Delayed Goblet Cell Hyperplasia, Acetylcholine Receptor Expression, and Worm Expulsion in SMC-Specific IL-4Rα–Deficient Mice

Interleukin 4 receptor alpha (IL-4Ralpha) is essential for effective clearance of gastrointestinal nematode infections. Smooth muscle cells are considered to play a role in the type 2 immune response-driven expulsion of gastrointestinal nematodes. Previous studies have shown in vitro that signal transducer and activator of transcription 6 signaling in response to parasitic nematode infection significantly increases smooth muscle cell contractility. Inhibition of the IL-4Ralpha pathway inhibits this response. How this response manifests itself in vivo is unknown. In this study, smooth muscle cell IL-4Ralpha-deficient mice (SM-MHC(Cre)IL-4Ralpha(-/lox)) were generated and characterized to uncover any role for IL-4/IL-13 in this non-immune cell type in response to Nippostrongylus brasiliensis infection. IL-4Ralpha was absent from alpha-actin-positive smooth muscle cells, while other cell types showed normal IL-4Ralpha expression, thus demonstrating efficient cell-type-specific deletion of the IL-4Ralpha gene. N. brasiliensis-infected SM-MHC(Cre)IL-4Ralpha(-/lox) mice showed delayed ability to resolve infection with significantly prolonged fecal egg recovery and delayed worm expulsion. The delayed expulsion was related to a delayed intestinal goblet cell hyperplasia, reduced T helper 2 cytokine production in the mesenteric lymph node, and reduced M3 muscarinic receptor expression during infection. Together, these results demonstrate that in vivo IL-4Ralpha-responsive smooth muscle cells are beneficial for N. brasiliensis expulsion by coordinating T helper 2 cytokine responses, goblet hyperplasia, and acetylcholine responsiveness, which drive smooth muscle cell contractions

Tradespace Investigation of a Telescope Architecture for Next-generation Space Astronomy and Exploration

Humanity’s endeavor to further its scientific understanding of the celestial heavens has led to the creation and evolution of increasingly powerful and complex space telescopes. Space telescopes provide a view of the solar system, galaxy, and universe unobstructed by Earth’s atmosphere and have profoundly changed the way people view space. In an effort to further advance space telescope capability and achieve the accompanying scientific understanding, the Massachusetts Institute of Technology (MIT), specifically, course 16.89 Space Systems Engineering, explored the tradespace of architectural enumerations encompassed within the design of an ultraviolet-optical-infrared (UVOIR) space telescope located at Sun-Earth Lagrangian Point Two (SE-L2). SE-L2 presents several advantages as an operating location for a UVOIR telescope such as a thermally stable environment and an orbit that allows the telescope to maintain a constant orientation with respect to all of the primary sources of heat and light. The main disadvantages associated with SE-L2 are caused by its relatively large distance from Earth, which marginalizes the effectiveness of real-time telerobotics because of latency and increases the cost of communications, launch, and servicing. Course 16.89 believes that, for this UVOIR application, the strengths of this operating location outweigh its weaknesses and therefore decided to explore the family of opportunities associated with SE-L2. This course used appropriate performance and system metrics to quantify the effectiveness of the aforementioned architectures and create a Pareto front of viable architectures. Evaluating the designs along the Pareto front allowed the course to characterize and group architectures and present these group-types to stakeholders for the selection of an optimal space telescope according to stakeholder requirements and resources. This course also developed sensitivity analysis, which allowed for a greater understanding of how architectural decisions affect the performance of the satellite. Segmentation, modularity, assembly, autonomy, and servicing were key aspects of this multidimensional analysis given the 16.8-meter class size and location of the telescope. Within the respective operating environment and for a spacecraft of similar characteristics, this model will allow stakeholders to predict the long-term operational effectiveness of different space telescope architectures and capture the synergistic effects of combining various architectural decisions into a spacecraft design. The following sections step through the aforesaid analysis and design efforts conducted in 16.89 beginning with Section III, which explicitly performs the stakeholder analysis and articulates the requirements of the mission. Section IV gives an overview of past designs and expands upon the architecture enumerations pertinent to this project, while Section V presents the methods and metrics by which those architectures will be evaluated and the system metrics which will be balanced and optimized in the creation of this space telescope. Section VI will present the model validation of this project and Section VII will discuss the results and analyses of the project. Finally, Section VIII will explore the future work opportunities of this project, while Section IX will present the conclusions and recommendations drawn from this project.MIT Department of Aeronautics and Astronautic

Delayed Goblet Cell Hyperplasia, Acetylcholine Receptor Expression, and Worm Expulsion in SMC-Specific IL-4Rα–Deficient Mice

Interleukin 4 receptor α (IL-4Rα) is essential for effective clearance of gastrointestinal nematode infections. Smooth muscle cells are considered to play a role in the type 2 immune response–driven expulsion of gastrointestinal nematodes. Previous studies have shown in vitro that signal transducer and activator of transcription 6 signaling in response to parasitic nematode infection significantly increases smooth muscle cell contractility. Inhibition of the IL-4Rα pathway inhibits this response. How this response manifests itself in vivo is unknown. In this study, smooth muscle cell IL-4Rα–deficient mice (SM-MHC(Cre)IL-4Rα(−/lox)) were generated and characterized to uncover any role for IL-4/IL-13 in this non–immune cell type in response to Nippostrongylus brasiliensis infection. IL-4Rα was absent from α-actin–positive smooth muscle cells, while other cell types showed normal IL-4Rα expression, thus demonstrating efficient cell-type–specific deletion of the IL-4Rα gene. N. brasiliensis–infected SM-MHC(Cre)IL-4Rα(−/lox) mice showed delayed ability to resolve infection with significantly prolonged fecal egg recovery and delayed worm expulsion. The delayed expulsion was related to a delayed intestinal goblet cell hyperplasia, reduced T helper 2 cytokine production in the mesenteric lymph node, and reduced M3 muscarinic receptor expression during infection. Together, these results demonstrate that in vivo IL-4Rα–responsive smooth muscle cells are beneficial for N. brasiliensis expulsion by coordinating T helper 2 cytokine responses, goblet hyperplasia, and acetylcholine responsiveness, which drive smooth muscle cell contractions

Novel sensor technology integration for outcome-based risk analysis in diabetes

Novel sensor-based continuous biomedical monitoring technologies have a major role in chronic disease management for early detection and prevention of known adverse trends. In the future, a diversity of physiological, biochemical and mechanical sensing principles will be available through sensor device 'ecosystems'. In anticipation of these sensor-based ecosystems, we have developed Healthcare@Home (HH) - a research-phase generic intervention-outcome monitoring framework. HH incorporates a closed-loop intervention effect analysis engine to evaluate the relevance of measured (sensor) input variables to system-defined outcomes. HH offers real-world sensor type validation by evaluating the degree to which sensor-derived variables are relevant to the predicted outcome. This 'index of relevance' is essential where clinical decision support applications depend on sensor inputs. HH can help determine system-integrated cost-utility ratios of bespoke sensor families within defined applications - taking into account critical factors like device robustness / reliability / reproducibility, mobility / interoperability, authentication / security and scalability / usability. Through examples of hardware / software technologies incorporated in the HH end-to-end monitoring system, this paper discusses aspects of novel sensor technology integration for outcome-based risk analysis in diabetes