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Laves phase plays a positive role in improving the strength of high-entropy alloys (HEAs); Nb and Ti elements have potential to promote Laves phase formation in some HEAs. For improving the strength of the face-centered cubic (FCC) CoCrFeMnNi HEA, a series of (CoCrFeMnNi)100−xNbx (atomic ratio: x = 0, 4, 8, 12, 16) and (CoCrFeMnNi)100−xTix (atomic ratio: x = 0, 2, 4, 6, 8, 12) HEAs were prepared by melting. The effects of Nb and Ti on the microstructure evolution and compressive properties of the CoCrFeMnNi HEAs were investigated. For (CoCrFeMnNi)100−xNbx HEAs, the second-phase (Laves and σ phase) volume fraction increased from 0 to 42%. The yield strength also increased gradually from 202 to 1010 MPa. However, the fracture strain decreased from 60% (no fracture) to 12% with increasing Nb content. For (CoCrFeMnNi)100−xTix HEAs, the yield strength increased from 202 to 1322 MPa. The Laves phase volume fraction also increased from 0 to 27%. However, the fracture strain decreased from 60% (no fracture) to 7.5% with increasing Ti content. Addition of Nb and Ti has a good effect on improving the strength of FCC CoCrFeMnNi HEA.
To assess the effect of famine exposure during early life on dietary patterns, chronic diseases, and the interaction effect between famine exposure and dietary patterns on chronic diseases in adulthood.
Cross-sectional study. Dietary patterns were derived by factor analysis. Multivariate quantile regression and log-binomial regression were used to evaluate the impact of famine exposure on dietary patterns, chronic diseases and the interaction effect between famine exposure and dietary patterns on chronic diseases, respectively.
Adults aged 45–60 years (n 939).
‘Healthy’, ‘high-fat and high-salt’, ‘Western’ and ‘traditional Chinese’ dietary patterns were identified. Early-childhood and mid-childhood famine exposure were remarkably correlated with high intake of the traditional Chinese dietary pattern. Compared with the non-exposed group (prevalence ratio (PR); 95 % CI), early-childhood (3·13; 1·43, 6·84) and mid-childhood (2·37; 1·05, 5·36) exposed groups showed an increased PR for diabetes, and the early-childhood (2·07; 1·01, 4·25) exposed group showed an increased PR for hypercholesterolaemia. Additionally, relative to the combination of non-exposed group and low-dichotomous high-fat and high-salt dietary pattern, the combination of famine exposure in early life and high-dichotomous high-fat and high-salt dietary pattern in adulthood had higher PR for diabetes (4·95; 1·66, 9·05) and hypercholesterolaemia (3·71; 1·73, 7·60), and significant additive interactions were observed.
Having suffered the Chinese famine in childhood might affect an individual’s dietary habits and health status, and the joint effect between famine and harmful dietary pattern could have serious consequences on later-life health outcomes.
Ti/Al/Mg/Al/Ti laminates were fabricated by hot rolling at 450 °C with various rolling reductions, and the relationship between the mechanical properties and microstructures was investigated in detail. Both Al–Mg and Ti–Al interfaces are well bonded without pore, crack, and intermetallics. Mg layer of 50% rolling reduction has the most dynamic recrystallized (DRXed) grains around the deformation bands, and tensile twins appear in Mg layer when the rolling reduction increases to 60%. Large numbers of twins are formed to absorb the further strain as reduction increases. Ti layer shows equiaxed grains, which are not sensitive to thickness strain. Mg layers of laminates with various rolling reductions all exhibit typical (0002) basal texture. Fifty-percent rolling reduction has the largest ultimate tensile strength of 337.8 MPa, which is mainly owing to grain refinement caused by the extensive DRX. The differences of elongation among the three samples with different rolling reductions are small.
Dilated Cardiomyopathy is a serious heart disorder that may induce sudden cardiac death and heart failure. Significant progress has been made in understanding the molecular basis of dilated cardiomyopathy. In previous studies, mutations in more than fifty genes have been identified in dilated cardiomyopathy patients. The purpose of this study was to detect the genetic lesion in a family from the central south of China affected by severe dilated cardiomyopathy.
Whole-exome sequencing combined with cardiomyopathy-related genes list were used to analyse the mutations of the proband. Co-segregation analysis was performed by Sanger sequencing.
Results and conclusions
Two novel heterozygous mutations – Myosin Binding Protein C: p.L1014RfsX6 and Titin: p.R9793X – were identified in the proband. The deletion mutation c.3041delT/p.L1014RfsX6 caused a premature stop codon at position 1020 in exon 28 of the Myosin Binding Protein C. The nonsense mutation, c.29377 C>T/ p. R9793X, of Titin was located in the highly evolutionarily conserved domain, resulting in truncation of the Titin protein as well. Co-segregation analysis further revealed that the Myosin Binding Protein C mutation came from his mother and the Titin mutation came from his father. Both mutations are reported in dilated cardiomyopathy patients for the first time. Our study not only provides a unique example of the genes and molecular mechanisms involved in dilated cardiomyopathy but also expands the spectrum of Myosin Binding Protein C and Titin mutations and contributes to the genetic diagnosis and counselling of dilated cardiomyopathy patients.
Specific adipokines, such as adiponectin and resistin, are secreted from adipose tissue and are associated with the development of obesity. Supplementation of dietary SCFA can prevent and reverse high-fat-diet (HFD)-induced obesity. However, it is not clear whether SCFA ameliorate abnormal expression of adiponectin and resistin in the obese state. The aim of this study was to investigate the effects of SCFA on adiponectin and resistin’s expressions in diet-induced obese mice, as well as the potential mechanisms associated with DNA methylation. C57BL/6J male mice were fed for 16 weeks with five types of HFD (34·9 % fat by wt., 60 % kJ) – a control HFD and four HFD with acetate (HFD-A), propionate (HFD-P), butyrate (HFD-B) and their admixture (HFD-SCFA). Meanwhile, a low-fat diet (4·3 % fat by wt., 10 % kJ) was used as the control group. The reduced mRNA levels of adiponectin and resistin in the adipose tissue of the HFD-fed mice were significantly reversed by dietary supplementation of acetate, propionate, butyrate or their admixture to the HFD. Moreover, the expressional changes of adiponectin and resistin induced by SCFA were associated with alterations in DNA methylation at their promoters, which was mediated by reducing the expressions of enzyme-catalysed DNA methyltransferase (DNMT1, 3a, 3b) and the methyl-CpG-binding domain protein 2 (MBD2) and suppressing the binding of these enzymes to the promoters of adiponectin and resistin. Our results indicate that SCFA may correct aberrant expressions of adiponectin and resistin in obesity by epigenetic regulation.
This study analyzed and assessed publication trends in articles on “disaster medicine,” using scientometric analysis. Data were obtained from the Web of Science Core Collection (WoSCC) of Thomson Reuters on March 27, 2017. A total of 564 publications on disaster medicine were identified. There was a mild increase in the number of articles on disaster medicine from 2008 (n=55) to 2016 (n=83). Disaster Medicine and Public Health Preparedness published the most articles, the majority of articles were published in the United States, and the leading institute was Tohoku University. F. Della Corte, M. D. Christian, and P. L. Ingrassia were the top authors on the topic, and the field of public health generated the most publications. Terms analysis indicated that emergency medicine, public health, disaster preparedness, natural disasters, medicine, and management were the research hotspots, whereas Hurricane Katrina, mechanical ventilation, occupational medicine, intensive care, and European journals represented the frontiers of disaster medicine research. Overall, our analysis revealed that disaster medicine studies are closely related to other medical fields and provides researchers and policy-makers in this area with new insight into the hotspots and dynamic directions. (Disaster Med Public Health Preparedness. 2019;13:165–172)
To produce pulses with good flat-top quality, pulse-forming lines (PFLs) have been widely used in the field of Tesla-type pulse generators. To shorten the physical length of the PFL, a double-width PFL (DWPFL) is proposed that doubles the output pulse width while maintaining flat-top quality. A repetitively 10 GW Tesla-type long-pulse generator producing pulses with flat-top width of about 110 ns was developed with a coaxial DWPFL to produce high-current electron beams. Electron beams of about 10 GW with flat-top widths of about 110 ns were obtained on a planar vacuum diode load. With this pulse generator and a C-band high-power microwave system, microwaves of ~2.2 GW power and full-width at half-maximum of 101 ns were generated. The experiment demonstrates the feasibility and ideal output waveform quality of the DWPFL.
SCN5A encodes sodium-channel α-subunit Nav1.5. The mutations of SCN5A can lead to hereditary cardiac arrhythmias such as the long-QT syndrome type 3 and Brugada syndrome. Here we sought to identify novel mutations in a family with arrhythmia.
Genomic DNA was isolated from blood of the proband, who was diagnosed with atrial flutter. Illumina Hiseq 2000 whole-exome sequencing was performed and an arrhythmia-related gene-filtering strategy was used to analyse the pathogenic genes. Sanger sequencing was applied to verify the mutation co-segregated in the family.
Results and conclusions
A novel missense mutation in SCN5A (C335R) was identified, and this mutation co-segregated within the affected family members. This missense mutation was predicted to result in amplitude reduction in peak Na+ current, further leading to channel protein dysfunction. Our study expands the spectrum of SCN5A mutations and contributes to genetic counselling of families with arrhythmia.
Syngas, predominantly a mixture of H2 and CO, is an important feedstock for the production of many valuable commodity chemicals such as methanol, synthetic liquid fuels, ammonia, and hydrogen. Since syngas forms the backbone of many chemical industries, its purity, H2:CO ratio, and cost have a major effect on the operation and economics of downstream chemical processing systems. Over the years, the process of syngas production has evolved from simply passing steam over hot coke to the use of large-scale solid circulating units that process a variety of hydrocarbon feedstocks. Some syngas production processes have been used at the commercial scale while others are still being developed at the lab and bench scale. Considerable knowledge has been gained from large-scale operations, and these have been valuable in paving the way for further innovations and new technologies development.
Gasification and reforming are the two processes that form the basis of all syngas production technologies. Syngas production technologies involve the use of oxidative reagents like oxygen, steam, CO2, and more recently metal oxide oxygen carriers, to selectively convert various hydrocarbon feedstocks to syngas. The term “selective” is significant since the formation of full combustion products, CO2 and H2O, is undesirable. Therefore, careful consideration is required when selecting operating conditions like temperature, pressure, catalyst, and/or metal oxide oxygen carriers. The ultimate goal for generating syngas is a process that is simple in operation and low in energy and cost requirements. For operation with metal oxides, as in chemical looping processes, combustion applications have been studied extensively. Relatively little has been probed on chemical looping gasification and reforming. There is a distinct difference in operating strategy between chemical looping gasification/chemical looping reforming (CLG/CLR) and chemical looping combustion (CLC) processes. The CLC processes can achieve a complete reactant gas oxidation with a low reactant gas to oxygen carrier ratio. The CLG/CLR processes, on the other hand, can achieve a partial or selective reactant fuel oxidation with a high reactant fuel to oxygen carrier ratio.
In this chapter, syngas generation technologies based on conventional processes and chemical looping processes are discussed. Specifically, Section 4.2 provides a historical viewpoint on the development of current commercial-scale syngas generation processes. An account of each of the technologies followed by examples of their application in commercial operation is given.
The conversion of carbonaceous feedstocks into higher value products occurs through two major routes: (1) indirect oxidation; and (2) direct oxidation, as shown in Figure 3.1. In the indirect oxidation approach, carbonaceous feedstock is first oxidized to syngas, which can then be further converted to value-added products. With respect to syngas generation, the thermodynamics and reaction characteristics of metal oxide oxygen carriers are discussed in Chapter 2; chemical looping reactor configurations are discussed in Chapter 4; and the techno-economic analyses of several chemical looping processes are discussed in Chapter 6. In the direct oxidation approach, the carbonaceous feedstock is directly upgraded to the desired product. Conceptually, the direct route simplifies the overall process and reduces costs by removing processing steps, but no commercial-scale system exists. Early research activity on direct oxidation processes, specifically for methane, can be traced back to the 1920s, but the utilization of methane in the chemical industry has been limited due to its high molecular stability. Currently, direct methane utilization involves conversion to value-added products such as aromatics, oxygenates, olefins, and paraffins, of which the three major oxidative processes are partial oxidation to methanol, to formaldehyde, as given in Section 5.4, and to ethylene and ethane via the oxidative coupling of methane (OCM).
Volatility in petroleum prices and limited petroleum reserves have made natural gas resources progressively more attractive as an energy source. Recent discoveries of natural gas reserves, increased accessibility to shale gas, and low natural gas prices have propelled a resurgence in methane-to-chemicals research. Monetizing cheap natural gas to obtain higher value-added products would provide a critical opportunity to the petroleum and chemical industry.9 Research into one promising direct route, OCM, has exhibited peaks and troughs, as shown in Figure 3.2. To date, pilot-scale systems were constructed and tested at the Atlantic Richfield Company (ARCO) in the 1990s. In 2012, Honeywell announced plans to scale up a proof-of-concept direct methane conversion process to ethylene. More recently, in 2015 Siluria Technologies began operating a pilot-scale OCM demonstration unit to convert methane to ethylene or gasoline.
In this chapter, the direct oxidation of methane to ethylene and higher hydrocarbons through OCM is presented.
Selective oxidation reactions of carbon based feedstocks synthesize important chemicals and their precursors, such as alcohols, epoxides, aldehydes, and other organic compounds. They employ catalytic metal oxides, which are multifunctional, enabling materials, to fulfill three parallel roles: (1) provide active surface sites for the reactants without participating in the reaction; (2) reduce the activation energies of the reaction pathway; and (3) oxidize the reactants through the transfer of their lattice oxygen during reduction. The third role is akin to the well-known catalytic surface Mars–Van Krevelen mechanism, which is further discussed in this section and Section 5.6, that is characterized by the reaction products incorporating the compounds of the catalytic material lattice. In these kinds of selective oxidation reactions, the catalytic metal oxides behave as “oxygen carriers,” where oxygen from the crystal lattice bonds with the reactants. In these reactions, the surface of the metal oxide is reduced by the hydrocarbon reactant and can later be re-oxidized by gaseous oxygen.
The selectivity of a catalytic metal oxide can be controlled by multiple factors, such as structure, chemistry, electronic properties, composition, kinetics, and energies. An ideal selective catalytic metal oxide needs to be tailored specifically for the application at hand. Hence, it becomes essential to understand the surface morphology, crystal structure, and the reaction mechanisms involved. The accessibility and mobility of lattice oxygen play a vital role in determining the reactivity and selectivity of the catalytic metal oxides. The structure of the catalytic metal oxide should allow for sufficient transportation of lattice oxygen toward the surface and needs to be able to sustain the vacancy created by the absence of oxygen. That is, the host structure needs to provide a sustainable pathway for the ions to diffuse in order to utilize the lattice oxygen. While participation of lattice oxygen facilitates the oxidation–reduction of the process, it does not necessarily result in high product selectivity. The selectivity of a given structure can originate from the bond strength between metal and oxygen, where a weak metal–oxygen bond will release oxygen that can fully oxidize the reactant and yield an undesired product. An ideal catalytic metal oxide with readily accessible and mobile lattice oxygen, appropriate host structure, and suitable metal–oxygen bond strength has the potential to be both reactive and selective when reduced.
This book is written as a sequel to an earlier book, entitled “Chemical Looping Systems for Fossil Energy Conversions,” published in 2010 by Wiley/AICHE. For the earlier book, the motivation was to elucidate the rationale for the resurgence of chemical looping technology research and development related to the ease in CO2 emission control and the enhancement in exergy conversion efficiency for combustion of carbonaceous fuels. The earlier book clearly indicated that the success of chemical looping technology depends strongly on the viability of the metal oxide materials for its redox applications. Knowledge of fundamental properties of these materials such as redox phase behavior, reactivity, recyclability, and metal oxide support is essential for characterizing chemical looping system performance for the conversion of coal, natural gas, petrochemicals, and biomass. Furthermore, it elaborated gasification or reforming processes involving syngas generation from traditional coal gasifiers, and the use of syngas as feedstock for hydrogen production through a steam–iron chemical looping reaction scheme. It also covered traditional methane–steam reforming applications that are coupled with chemical looping heating schemes, followed by water–gas shift reactions for hydrogen generation. Chemical looping process simulations based on Aspen Plus® utilizing reactors such as gasifier, reducer, oxidizer, combustor, and processes such as conventional gasification and chemical looping for electricity and liquid fuel production were presented.
My motivation for writing this book was precipitated by the exciting recent revelation of direct, one-step, chemical looping partial oxidation techniques in gasifiers and reformers using carbonaceous feedstock. These techniques can produce syngas of a high quality, leading to process efficiencies far greater than any traditional gasification or reforming techniques and other chemical looping techniques. The implications of this discovery are significant in that syngas compositions can reach to near the thermodynamic conversion limit with a H2:CO molar ratio that can readily be used for direct downstream chemicals or liquid fuels synthesis. The uniqueness of these gasification and reforming techniques is that the syngas stream from the chemical looping reducer reactor will contain little CO2, yielding a process of high carbon utilization efficiency. Even higher carbon utilization efficiencies can be achieved in a chemical looping process scheme for chemicals or liquid fuels production when the CO2 generated from the process system can be fully recycled to the reducer reactor, yielding a CO2 neutral chemical looping process system.
A process simulation is the representation of a thermal or chemical transformation by a mathematical model that is solved to provide information about mass and energy requirements, equipment performance, and overall process feasibility. They are system level models used for economic calculations, energy efficiency analyses, and process comparisons. Component level information such as reactor geometry, mixing and hydrodynamics, and transport phenomena, as well as molecular level information such as surface area, reaction mechanism, and electronic interactions, are not included. Beginning with FlowTran, developed by Monsanto in the 1950s and 1960s, several process simulation software packages have since been developed, including ProSim, PRO/II, gPROMS, ChemCAD, and Aspen Plus®, and they play an important role in process development by allowing for the evaluation of a commercial scale plant based on available experimental results.
The process simulation software that is used extensively throughout academic research and industrial operations is Aspen Plus®. Aspen was developed in the late 1970s at Massachusetts Institute of Technology for the United States Energy Research and Development Administration (now United States Department of Energy or USDOE). The project objective was to develop a computer program to aid in performing process evaluations; mainly process economics. Today, Aspen has evolved into Aspen Plus® and, as part of the AspenOne package software suite, has become the essential plant and process design software program. Aspen Plus® provides complete flexibility in designing a process simulation. Every new process begins by specifying the component species and the property method used for calculating the component species thermodynamic properties. Together, these two required specifications display the strength of the Aspen Plus® software program, due to its extensive chemical databank, available methods for calculating thermodynamic properties, and ability to adjust property values when necessary. Once the component species and property methods have been selected, Aspen Plus® assumes control and calculates the thermodynamic properties based on user input, and only allows the inputs required to satisfy the degrees of freedom. The chemical looping partial oxidation examples and the results presented in this chapter were obtained using Aspen Plus® (AspenTech), and they are available on the website as supplemental material.