Highly reactive metastable intermixed composites (MICs) have attracted much attention in the past decades. The MIC family of materials mainly includes traditional metal‐based nanothermites, novel ...core–shell‐structured, 3D ordered macroporous‐structured, and ternary nanocomposites. By applying special fabrication approaches, highly reactive MICs with uniformly dispersed reactants, “layer‐by‐layer” or “core–shell” structures, can be prepared. Thus, the combustion performance can be greatly improved, and the ignition characteristics and safety can be precisely controlled by using a certain preparation strategy. Here, the preparation and characterization of the MICs that have been developed during the past few decades are summarized. Traditional preparation methods for MICs generally include physical mixing, high‐energy ball milling, sol–gel synthesis, and vapor deposition, while the novel methods include self‐assembly, electrophoretic deposition, and electrospinning. Various preparation procedures and the ignition and combustion performance of different MIC reactive systems are compared and discussed. In particular, the advantages of novel structured MICs in terms of safety and combustion efficiency are clarified, based on which suggestions regarding the possible future research directions are proposed.
Highly reactive metastable intermixed composites (MICs) prepared by different strategies show various characteristics and properties. By applying special fabrication approaches, highly reactive MICs with uniformly dispersed reactants, assembled in either layer‐by‐layer or core–shell structure, can be prepared. Thus, the improved and desired performances can be achieved by using a certain preparation strategy.
Transition‐metal‐catalyzed difluoroalkylation of aromatics remains challenging despite the importance of difluoroalkylated arenes in medicinal chemistry. Herein, the first successful example of ...nickel‐catalyzed difluoroalkylation of aryl boronic acids is described. The reaction allows access to a variety of functionalized difluoromethyl bromides and chlorides, and paves the way to highly cost‐efficient synthesis of a wide range of difluoroalkylated arenes. The notable features of this protocol are its high generality, excellent functional‐group compatibility, low‐cost nickel‐catalyst, and practicality for gram‐scale production, thus providing a facile method for applications in drug discovery and development.
Simple and easy: The first example of a nickel‐catalyzed difluoroalkylation of aryl boronic acids with functionalized difluoromethyl bromides and chlorides has been developed. This cross‐coupling process features a broad substrate scope, a cheap catalyst, and excellent functional‐group compatibility.
The Tian Shan of Central Asia is located in the southwestern part of the Central Asian Orogenic Belt (CAOB, also known as the Central Asian Orogenic System or CAOS). Formation of the South Tian Shan ...Orogen is a diachronous, scissors-like process during the Paleozoic and its western segment in China–Kyrgyzstan contiguous regions is accepted as the site of the final collision zone between the Tarim craton to the south and the Kazakhstan–Yili terrane to the north in the Late Paleozoic. However, when the final collision occurred is still in hot debate. Particularly, an end-Permian to Triassic collisional model is recently proposed for the western segment of the South Tian Shan Orogen. This even leads to the speculation that the complicated accretion–collision processes in the Northern Xinjiang of western China, which involved the terrane amalgamation in the East and West Junggar and the collision between the Altai and Kazakhstan terranes and between the Yili–Central Tian Shan and Junggar terranes, were finally terminated during the end-Permian to mid-Triassic, rather than the Late Paleozoic as usually accepted. Obviously, the western segment of the South Tian Shan Orogen also presents the key issue associated with the termination time of accretion–collision processes in the Northern Xinjiang. A collisional model that is derived from the knowledge of the Himalayan Orogen is helpful for establishing a sequence of major tectonothermal events in the western segment of the South Tian Shan Orogen and constraining the time of collision between the Tarim craton and the Kazakhstan–Yili terrane.
For the western segment of the South Tian Shan Orogen, the end-Permian to Triassic collisional model is mainly based on Triassic zircon U–Pb ages of 234 to 226
Ma from the West Tian Shan eclogite and two suspected Late Permian radiolarian specimens
Albaillella excelsa Ishiga, Kito and Imoto (?) from the Baleigong ophiolitic mélange. Actually, the poor preservation of the two radiolarian specimens and the lack of a ventral wing make their identifications difficult. Furthermore, the Baleigong ophiolitic mélange was intruded by one granite pluton with a zircon age of 273
Ma, and this provides geological evidence against the reliability of the Late Permian radiolarian specimens. Because the Triassic zircons contain no index mineral inclusions such as omphacite and coesite grown under high to ultrahigh pressure conditions, it is difficult to link their ages to high to ultrahigh pressure peak metamorphism. In addition, this model is not compatible with extensive Permian plutonism and molasse sedimentation and Triassic to Jurassic tectonomagmatic quiescence and continental deposits in the collisional zone and adjacent tectonic units.
In contrast, new U–Pb ages of the zircon domains containing omphacite and phengite inclusions and Sm–Nd and rutile U–Pb ages of eclogite samples from the western segment of the South Tian Shan Orogen consistently indicate that high pressure peak metamorphism of subducted oceanic material occurred at ~
319
Ma (the end of the Early Carboniferous). This and the youngest Early Carboniferous radiolarian and conodonts fossils from ophiolitic mélanges show that the collision must have taken place after the Early Carboniferous, whereas the oldest stitching granitic plutons in the collisional zone place an upper-age bound of ~
300
Ma (the end of the Late Carboniferous) for the collision. These specify that the final collision in the western segment of the South Tian Shan took place in the Late Carboniferous rather than the end-Permian to Triassic. Noticeably, syn-collisional granitoids are rare, but Permian post-collisional plutonism and molasse sedimentation are widespread in the western segment of the South Tian Shan and adjacent tectonic units, and the oldest post-collisional plutons were nearly concurrent with low pressure, high temperature metamorphism in the south edge of the Kazakhstan–Yili terrane. All these suggest a significant geodynamic change at ~
300
Ma, which may be caused by delamination of the thickened lithospheric root and asthenospheric upwelling. Such a process might have provided heat for low pressure, high temperature metamorphism and triggered partial melting of the lower crust and underlying lithosphere in the western segment of the South Tian Shan Orogen and adjacent tectonic units. The Late Carboniferous collisional model is also compatible with the Triassic to Jurassic tectonomagmatic quiescence and continental deposits in the western segment of the South Tian Shan Orogen and adjacent tectonic units.
For the South Tian Shan Orogen, the final collision in the western segment occurred in the Late Carboniferous, significantly younger than that in the eastern segment. In the Northern Xinjiang, the Late Carboniferous collision in the western segment of the South Tian Shan Orogen was nearly simultaneous with the final collision in the North Tian Shan collisional zone between the Yili–Central Tian Shan and Junggar terranes and in the Irtysh–Zaysan collisional zone between the Altai and Kazakhstan terranes, and these collisional events postdated the terrane amalgamation in the East and West Junggar. Therefore, the accretion–collision processes in the Northern Xinjiang were finally terminated during the Late Carboniferous rather than the end-Permian to mid-Triassic.
Spasm of arterial grafts in coronary artery bypass grafting surgery is still a clinical problem, and refractory spasm can occasionally be lethal. Perioperative spasm in bypass grafts and coronary ...arteries has been reported in 0.43% of all coronary artery bypass grafting surgery, but this may be an underestimate. Spasm can develop not only in the internal mammary artery but more frequently in the right gastroepiploic and radial artery. The mechanism of spasm can involve many pathways, particularly those involving regulation of the intracellular calcium concentration. Endothelial dysfunction also plays a role in spasm. Depending on the clinical scenario, the possibility of spasm during and after coronary artery bypass grafting should be confirmed by angiography. If present, immediate intraluminal injection of vasodilators is often effective, although other procedures such as an intraaortic balloon pump or extracorporeal membrane oxygenation may also become necessary to salvage the patient. Prevention of spasm involves many considerations, and the principles are discussed in this review article.
Abstract Background Pathogenesis and diagnostic biomarkers for diseases can be discovered by metabolomic profiling of human fluids. If the various types of coronary artery disease (CAD) can be ...accurately characterized by metabolomics, effective treatment may be targeted without using unnecessary therapies and resources. Objectives The authors studied disturbed metabolic pathways to assess the diagnostic value of metabolomics-based biomarkers in different types of CAD. Methods A cohort of 2,324 patients from 4 independent centers was studied. Patients underwent coronary angiography for suspected CAD. Groups were divided as follows: normal coronary artery (NCA), nonobstructive coronary atherosclerosis (NOCA), stable angina (SA), unstable angina (UA), and acute myocardial infarction (AMI). Plasma metabolomic profiles were determined by liquid chromatography–quadrupole time-of-flight mass spectrometry and were analyzed by multivariate statistics. Results We made 12 cross-comparisons to and within CAD to characterize metabolic disturbances. We focused on comparisons of NOCA versus NCA, SA versus NOCA, UA versus SA, and AMI versus UA. Other comparisons were made, including SA versus NCA, UA versus NCA, AMI versus NCA, UA versus NOCA, AMI versus NOCA, AMI versus SA, significant CAD (SA/UA/AMI) versus nonsignificant CAD (NCA/NOCA), and acute coronary syndrome (UA/AMI) versus SA. A total of 89 differential metabolites were identified. The altered metabolic pathways included reduced phospholipid catabolism, increased amino acid metabolism, increased short-chain acylcarnitines, decrease in tricarboxylic acid cycle, and less biosynthesis of primary bile acid. For differential diagnosis, 12 panels of specific metabolomics-based biomarkers provided areas under the curve of 0.938 to 0.996 in the discovery phase (n = 1,086), predictive values of 89.2% to 96.0% in the test phase (n = 933), and 85.3% to 96.4% in the 3-center external sets (n = 305). Conclusions Plasma metabolomics are powerful for characterizing metabolic disturbances. Differences in small-molecule metabolites may reflect underlying CAD and serve as biomarkers for CAD progression.
Summary
During infection, intracellular pathogens inevitably face the pressure of hypoxia. Mycobacterium tuberculosis and Mycobacterium bovis represent two typical intracellular bacteria, but the ...signalling pathway of their adaptation to hypoxia remains unclear. Here, we report a new mechanism of the hypoxic adaptation in M. bovis driven by the second messenger molecule c‐di‐GMP. We found that c‐di‐GMP was significantly accumulated in bacterial cells under hypoxic stress and blocked the inhibitory activity of ArgR, an arginine metabolism gene cluster regulator, which increased arginine synthesis and slowed tricarboxylic acid cycle (TCA cycle) and aerobic respiration. Meanwhile, c‐di‐GMP relieved the self‐inhibition of argR expression, and ArgR could interact with the nitrite metabolic gene regulator Cmr, promoting the positive regulation of Cmr and, thereafter, the nitrite respiration. Consistently, c‐di‐GMP significantly induced the expression of arginine and nitrite metabolism gene clusters and increased the mycobacterial survival ability under hypoxia. Therefore, we found a new function of the second messenger molecule c‐di‐GMP and characterized ArgR as a metabolic switching regulator that can coordinate the c‐di‐GMP signal to trigger hypoxic adaptation in mycobacteria. Our findings provide a potential new target for blocking the life cycle of M. tuberculosis infection.
Among the various types of metal matrix composites, SiC particle-reinforced aluminum matrix composites (SiC
p
/Al) are finding increasing applications in many industrial fields such as aerospace, ...automotive, and electronics. However, SiC
p
/Al composites are considered as difficult-to-cut materials due to the hard ceramic reinforcement, which causes severe machinability degradation by increasing cutting tool wear, cutting force, etc. To improve the machinability of SiC
p
/Al composites, many techniques including conventional and nonconventional machining processes have been employed. The purpose of this study is to evaluate the machining performance of SiC
p
/Al composites using conventional machining, i.e., turning, milling, drilling, and grinding, and using nonconventional machining, namely electrical discharge machining (EDM), powder mixed EDM, wire EDM, electrochemical machining, and newly developed high-efficiency machining technologies, e.g., blasting erosion arc machining. This research not only presents an overview of the machining aspects of SiC
p
/Al composites using various processing technologies but also establishes optimization parameters as reference of industry applications.
High-entropy ceramics exhibit great application potential as thermal barrier coating (TBC) materials. Herein, a series of novel high-entropy ceramics with RE2(Ce0.2Zr0.2Hf0.2Sn0.2Ti0.2)2O7 (RE2HE2O7, ...RE = Y, Ho, Er, or Yb) compositions were fabricated via a solid-state reaction. X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) mapping analyses confirmed that RE2HE2O7 formed a single defect fluorite structure with uniform elemental distribution. The thermophysical properties of the RE2HE2O7 ceramics were investigated systematically. The results show that RE2HE2O7 ceramics have excellent high-temperature phase stability, high thermal expansion coefficients (10.3–11.7 × 10−6 K-1, 1200 ℃), and low thermal conductivities (1.10-1.37 W m-1 K-1, 25 ℃). In addition, RE2HE2O7 ceramics have a high Vickers hardness (13.7–15.0 GPa) and relatively low fracture toughness (1.14-1.27 MPa m0.5). The outstanding properties of the RE2HE2O7 ceramics indicate that they could be candidates for the next generation of TBC materials.
Abstract
It is widely accepted that quite a number of double compact objects (DCOs) in the Milky Way can be identified by future space-based gravitational wave (GW) detectors, while systematic ...investigations on the detection of the GW sources in nearby galaxies are still lacking. In this paper, we present calculations of potential populations of GW sources for all types of DCOs in the Local Group galaxy M31. For M31, we use an age-dependent model for the evolution of the metallicity and the star formation rate. By varying assumptions of common-envelope ejection efficiencies and supernova-explosion mechanisms during binary evolution, we make predictions on the properties of DCOs that can be detected by the Laser Interferometer Space Antenna (LISA). Our calculations indicate that a few (a dozen) DCOs are likely to be observed by LISA during its 4 (10) yr mission. We expect that the sources with black hole components are more likely to be first identified during a 4 yr mission since these binaries have relatively large chirp masses, while the systems with white-dwarf components dominate the overall population of detectable GW sources during a 10 yr mission. LISA can only detect very tight fast-merging systems in M31, corresponding to the peak of orbital period distribution from ∼2 minutes for double white dwarfs to ∼20 minutes for double black holes.
Low‐cost and flexible panchromatic organic photodetectors (OPDs) are one of the most promising alternatives in next‐generation wearable electronics, but they still face the formidable challenges of ...replacing brittle indium tin oxide electrode and suffer from low near‐infrared (NIR) photo‐response. Herein, the low‐cost metal copper (Cu) is used as a semi‐transparent anode to fabricate high‐performance panchromatic multiplication‐type OPDs. Because of the advantages of smooth surface, lower sheet resistance, and good transmittance, high‐quality optical resonant cavity forming between Cu anode and aluminum cathode greatly enhanced the weak sub‐bandgap response of intermolecular charge transfer states in NIR region, while also retaining a good response in the UV–vis region. Due to the good hole‐collecting ability, the Cu electrode is suitable for realizing the photo‐multiplication effect. Accordingly, the resulting OPDs achieve a panchromatic response ranging from the UV (300 nm) to NIR (900 nm) region. The maximum external quantum efficiency (EQE) reaches 117 040% at 350 nm, and the relatively high EQE of 25 468% is realized even at 765 nm. Furthermore, a flexible OPD is successfully fabricated by using polyethylene terephthalate substrate with Cu anode to achieve the real‐time detection of human blood oxygen pulse signals.
A microcavity structure based on a low‐cost copper semi‐transparent electrode is adopted to manipulate the optical field distribution in organic photodetectors and enhance the absorption of intermolecular charge transfer states in the near‐infrared region to broaden the device response range. The introduction of the multiplication mechanism greatly improves the external quantum efficiency of the device, and finally yields high‐performance panchromatic organic photodetectors.
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