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The RBCC (rocket-based combined-cycle) engine integrates a rocket engine into the flow passage of the ramjet engine, thereby significantly broadening the operating range and becoming one of the potential solutions for the reusable space transportations. The embedded rocket, as one of the core components of an RBCC engine, is strongly coupled to other components, such as the inlet and combustor, and can induce significant impacts on the inlet start behaviors. For the stable operation of the RBCC inlet, the start/unstart hysteresis characteristics and the reliable start boundaries driven by embedded rocket are experimentally and numerically studied. The results show that due to the function of embedded rocket jet, the inlet start/unstart hysteresis range of Mach number rises from Mach 1.79–1.87 to 1.85–1.90, and the back pressure hysteresis range changes from Pc/P∞ of 3.9–5.8 to 4.7–5.8. Meanwhile, during the increasing and decreasing process of the embedded rocket pressure, the inlet undergoes a transition between start and unstart, accompanied by hysteresis phenomena as well. Furthermore, three different control strategies are proposed for the start of RBCC inlet. Similar to the traditional ramjet inlets, the RBCC inlet can self-/re-start by reducing the back pressure. Particularly, owing to the synergistic effect of embedded rocket jet and back pressure, the RBCC inlet can self-/re-start by reducing the embedded rocket pressure from Procket/P∞ = 58 to 39 in the "embedded rocket dominated" cases, while the inlet self-/re-start can be achieved by increasing the rocket pressure from Procket/P∞ = 20 to 39 in the "back pressure dominated" cases. [ABSTRACT FROM AUTHOR]

The dynamic flow behaviors, as well as the propagation and coupling of regulation information, in a rocket-based combined-cycle inlet isolator during the ejector-to-ramjet mode transitions driven by different embedded rocket control methods, are numerically investigated. The key parameters of compression power, Mach number, and pressure ratio are used to illustrate the operation performance of the inlet isolator. The rocket jet induces strong shocks while inhibiting the shock/boundary layer interaction in the jet-covered region. The coupling of the rocket jet shear and back pressure is linked to the formation of wall flow separation. The parameter distributions are greatly influenced by the destruction of shock structures, which is crucial for the stability of supersonic flowfields. The continuity of the jet boundary is disrupted by the regulation of the embedded rocket, and an increase in the throttle level will further intensify the breakup. Back pressure propagation is limited by the rocket jet and is constantly matched with the jet and mainstream until the rocket's influence domain reaches stable. The "high throttle-maintaining" and "direct-shutdown" mode transitions tend to induce oscillations in the isolator compression performance. In the "direct-shutdown" mode transition, the vorticity proportion in the combustor is unstable and the flowfield disorder is high. In the "high throttle-maintaining" mode transition, the vortex generation level is relatively stable and high, while the entropy proportion fluctuates strongly and at a high level. By adopting the "medium throttle-maintaining" mode transition, the entropy and vorticity proportion levels are relatively stable, which is conducive to the stability of mode transition. [ABSTRACT FROM AUTHOR]

The spatiotemporal distribution characteristics and flow stability of a rocket-based combined-cycle (RBCC) inlet during the ejector-to-ramjet mode transition are investigated numerically. The operational pressure of the embedded rocket is adjusted to three different levels, and the time-sequences of the rocket and back pressure regulation are varied. The pressure in feature sections is monitored to reveal the coupling relationship and stability of the internal flowfield. The inlet is more adaptable to severe disturbances under the "throttle-maintaining" regulation and is susceptible under the "direct-shutdown" regulation. The severe fluctuation period is relatively short within "medium throttle-maintaining," while is lengthy within the "high throttle-maintaining." The severe fluctuation under the direct-shutdown develops with the propagation of the regulation and decays with its establishment. The ultimate flowfields driven by different time-sequences reach unanimity with the same adjustable parameters of embedded rocket and back pressure; however, the dynamic evolutions show distinct characteristics. During the mode transition, pressure "valleys" are formed in any selected sections with the rocket regulations, and "peaks" are developed in many sections due to the propagation of back pressure or the instability of the rocket jet. For the medium throttle-maintaining regulation, the effect of time-sequence on the flowfield is relatively weak. For the high throttle-maintaining regulation, the pressure disturbance rises abruptly under the rocket priority regulation, with a most severe amplitude of 100.7%. For the direct-shutdown regulation, the maximum pressure disturbance of 125% is observed within the rocket priority regulation, and the minimum disturbance occurs within the back pressure priority regulation. [ABSTRACT FROM AUTHOR]

This paper investigates conditional configurations for improving high‐tech enterprises' new product development (NPD) performance under complex environment of digital era in China. The results indicate that digital transformation is neither sufficient nor necessary for high NPD performance but a significant component of those configurations for high NPD performance. Through the fuzzy‐set qualitative comparative analysis (fsQCA) approach, four configurations for high NPD performance and four configurations for non‐high NPD performance are generated from complex nonlinear interactions among five antecedent conditions of NPD performance. Our findings enrich the literature on NPD performance and provide references on enterprises' decision making on digital transformation. [ABSTRACT FROM AUTHOR]

Motivation The discovery of the genetic features that underly a phenotype is a fundamental task in microbial genomics. With the growing number of microbial genomes that are paired with phenotypic data, new challenges, and opportunities are arising for genotype-phenotype inference. Phylogenetic approaches are frequently used to adjust for the population structure of microbes but scaling them to trees with thousands of leaves representing heterogeneous populations is highly challenging. This greatly hinders the identification of prevalent genetic features that contribute to phenotypes that are observed in a wide diversity of species. Results In this study, Evolink was developed as an approach to rapidly identify genotypes associated with phenotypes in large-scale multispecies microbial datasets. Compared with other similar tools, Evolink was consistently among the top-performing methods in terms of precision and sensitivity when applied to simulated and real-world flagella datasets. In addition, Evolink significantly outperformed all other approaches in terms of computation time. Application of Evolink on flagella and gram-staining datasets revealed findings that are consistent with known markers and supported by the literature. In conclusion, Evolink can rapidly detect phenotype-associated genotypes across multiple species, demonstrating its potential to be broadly utilized to identify gene families associated with traits of interest. Availability and implementation The source code, docker container, and web server for Evolink are freely available at https://github.com/nlm-irp-jianglab/Evolink. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction technology that uses CO as a reductant (CO-SCR) has great potential in addressing nitrogen oxides (NOx) pollution in industry. Herein, we reported the in situ growth of highly efficient CuMnO2 nanosheet catalysts on low-cost stainless steel mesh (SSM) by a hydrothermal method, which exhibited excellent CO-SCR performance. It has been demonstrated that the prepared CuMnO2 nanosheet catalysts with high crystallinity and an exposed (001) plane could realize 100% NO conversion and N2 selectivity at 310 °C, which is comparable to other reported Cu–Mn–O catalysts. Moreover, the reaction mechanism driven by the surface synergetic oxygen vacancy of Cu–□–Mn is also proposed for enhancement of the CO-SCR performance. The good mechanical strength, easy shape processability, and high temperature stability of the inexpensive SSM support, together with the good catalytic performance of the active CuMnO2 component, could make the CuMnO2/SSM monolithic catalyst more favorable for large-scale industry application in de-NOx. [ABSTRACT FROM AUTHOR]

A rocket-based combined-cycle (RBCC) inlet is always required to start at a relatively low Mach number in consideration of the fuel consumption in the ejector mode and the comprehensive engine performance throughout the flight trajectory. However, the practical start of an RBCC inlet is a dynamic process easily and significantly affected by the embedded rocket operating at a high chamber pressure in the ejector mode. Thus, the real start limits, in terms of the Kantrowitz limit and isentropic limit, and the relevant operational characteristics in the practical applications of a central strut–based RBCC inlet were studied through theoretical analysis and numerical simulations. A two-dimensional analysis model of the RBCC inlet fully concerning the expansion and aerodynamic compression of the rocket jet was established, and the theoretical calculation methods for the inlet start limits were carefully validated and corrected through numerical simulations. It was found that the underexpanded rocket jet expanded rapidly outside the nozzle and compressed the aerodynamic configuration of the flow passage, thereby increasing the actual internal compression ratio (ICR) of the RBCC inlet and increasing the difficulty of the start. The influence rules of the operational pressure and the nozzle expansion angle of the embedded rocket on the RBCC inlet start limits were also theoretically studied. As these key parameters kept increasing, the start limits were increased gradually. Moreover, the isentropic limit was more sensitive to the operational chamber pressure, whereas the increasing rate of the Kantrowitz limit was much more sensitive to the enlarging nozzle expansion angle. Finally, a positive control method based on the rocket operation during the inlet start process was promoted, which could not only guarantee the self-start requirement of the RBCC inlet as the designed scheme in the practical operation, but could also improve the compression efficiency and back-pressure resistance effectively in the subsequent ramjet operation. [ABSTRACT FROM AUTHOR]

LIGO-Virgo has observed the gravitational waves (GWs) from the coalescence of binary black hole (BBH) and binary neutron star (BNS) during O1 and O2, and the ones from NS-BH are expected to be hunted in the operating O3 run. The population properties and mass distribution of NS-BH mergers are poorly understood now, thus researchers simulated their chirp mass ( â„ł) distribution by a synthetic model, in which the BHs and NSs were inferred by LIGO-Virgo (O1/O2), and obtained the values in the range of 2.1 M ⊙ < â„ł < 7.3 M ⊙ . In this paper, we further simulate the GW frequency (f GW) distribution of NS-BH mergers by the above-stated synthetic model, with a basic binary system model through the Monte Carlo method. Our results predict that the median with 90% credible intervals is 165 âˆ' 64 + 475 Hz in the case of Schwarzschild BH when the system just before merger, and this GW frequency is expected to increase several times in the merger stage, which is lying in the frequency band of LIGO-Virgo, i.e., about 15 Hz to a few kHz. Our results provide an important reference for hunting the NS-BH mergers by the on-going O3 run of LIGO-Virgo. [ABSTRACT FROM AUTHOR]

Primordial nitrification processes have been studied extensively using geochemical approaches, but the biological origination of nitrification remains unclear. Ammonia-oxidizing archaea (AOA) are widely distributed nitrifiers and implement the rate-limiting step in nitrification. They are hypothesized to have been important players in the global nitrogen cycle in Earth's early history. We performed systematic phylogenomic and marker gene analyses to elucidate the diversification timeline of AOA evolution. Our results suggested that the AOA ancestor experienced terrestrial geothermal environments at ∼1,165 Ma (1,928–880 Ma), and gradually evolved into mesophilic soil at ∼652 Ma (767–554 Ma) before diversifying into marine settings at ∼509 Ma (629–412 Ma) and later into shallow and deep oceans, respectively. Corroborated by geochemical evidence and modeling, the timing of key diversification nodes can be linked to the global magmatism and glaciation associated with the assembly and breakup of the supercontinent Rodinia, and the later oxygenation of the deep ocean. Results of this integrated study shed light on the geological forces that may have shaped the evolutionary pathways of the AOA, which played an important role in the ancient global nitrogen cycle. [ABSTRACT FROM AUTHOR]

The elderly usually suffer from many diseases. Improving the quality of life of the elderly is an urgent social issue. In this present study, D-galactose treated aging mice models were used to reveal the effects of different animal sources and different doses of whey protein (WP) on the immune indexes organs and intestinal flora. A total of 9 groups were set up, including normal control (NC), negative control (NS), positive control (Vc), low-, medium- and high-doses of cow WP intervention groups (CL, CM and CH for short, correspondingly) and low-, medium- and high-doses of goat WP intervention groups (GL, GM and GH for short, correspondingly). The body weight gain, thymus/body weight ratio, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, spleen immunoglobulins G (IgG), spleen interleukin-2 (IL-2) and spleen interleukin-2 (IL-6) were measured. Then, the intestinal contents were collected, and 16s genes of intestinal bacteria were sequenced to reveal the changes in bacterial flora structure. WP intervention significantly increased the weight gain, thymus/body ratio and SOD activity, but decrease the content of MDA. WP intervention increased some immune indicators. All the WP treated aging mice showed similar values of physiological indexes to that of the Vc group, even better. The relative abundance of Lactobacillus and Stenotrophomonas was increased and decreased, respectively, by both cow and goat WP. Lactobacillus may be involved in regulating the functional repair of organisms. In contrast, Stenotrophomonas might play a negative role in the immune and antioxidant capacity of the body. Combining physiological indicators and intestinal flora structure, low-concentration WP for cow and goat might be optimal for aging models. [ABSTRACT FROM AUTHOR]

Novel coronaviruses, including SARS-CoV-2, SARS, and MERS, often originate from recombination events. The mechanism of recombination in RNA viruses is template switching. Coronavirus transcription also involves template switching at specific regions, called transcriptional regulatory sequences (TRS). It is hypothesized but not yet verified that TRS sites are prone to recombination events. Here, we developed a tool called SuPER to systematically identify TRS in coronavirus genomes and then investigated whether recombination is more common at TRS. We ran SuPER on 506 coronavirus genomes and identified 465 TRS-L and 3,509 TRS-B. We found that the TRS-L core sequence (CS) and the secondary structure of the leader sequence are generally conserved within coronavirus genera but different between genera. By examining the location of recombination breakpoints with respect to TRS-B CS, we observed that recombination hotspots are more frequently colocated with TRS-B sites than expected. [ABSTRACT FROM AUTHOR]

The merger event of double neutron star (DNS) system (GW170817) was detected by the gravitational-wave (GW) detectors (Advanced LIGO and Advanced Virgo) in 2017 for the first time, so their mass distribution has become a significant topic with the new round GW hunting (O3) in 2019. A few models (e.g. Gaussian, two-Gaussian, or mixture-Gaussian) were adopted to draw the mass distribution of observed Galactic DNS systems, however, there is no a confirmed model now due to the small size of DNS samples (N  < 20). Here we focus on determining the most probable distribution ranges of DNS masses without model selection by assuming the neutron star masses to be uniformly distributed between the lower and upper bounds. We apply a Bayesian analysis and Markov chain Monte Carlo simulation to 15 Galactic DNS systems, and obtain that the component masses of DNS systems should mainly fall in the range of 1.165–1.590 M⊙, and the predominant ranges for the total mass, mass ratio, and chirp mass lie in 2.535–2.867 M⊙, 0.741–0.995, and 1.115–1.237 M⊙, respectively. Our results are in agreement with the properties of DNS in GW170817, whose 90 per cent credible intervals for the component masses, total masses, mass ratio, and chirp masses are 1.16–1.60 M⊙, |$2.73_{-0.01}^{+0.04}\, \mathrm{ M}_\odot$|⁠ , 0.73–1.00, and |$1.186_{-0.001}^{+0.001}\, \mathrm{ M}_\odot$|⁠ , respectively. The above similarity is an important indicator that reveals the source of GW170817 to be a DNS system from the galaxy NGC 4993, and our results can be tested by the forthcoming GW hunting O3. [ABSTRACT FROM AUTHOR]

For the observed 18 pairs of double neutron star (DNS) systems, we find that DNS mass distribution is very narrow and its mean value (about 1.34 solar mass) is less than the mean of all measured pulsars of about 1.4 solar mass. To interpret the special DNS mass characteristics, we analyze the DNS formation process, via the phases of HMXBs, by investigating the evolution of massive binary stars. Moreover, in DNSs, two classes of NSs are taken into account, formed by supernova (SN) and electron capture (EC), respectively, and generally the NS mass by SN is bigger than that by EC. Quantitatively, with various initial conditions of binary stars, the observed special DNS distribution can be satisfactorily explained. [ABSTRACT FROM AUTHOR]

Despite the high specificity between antigen and antibody binding, similar epitopes can be recognized or cross-neutralized by paratopes of antibody with different binding affinities. How to accurately characterize this slight variation which may or may not change the antigen-antibody binding affinity is a key issue in this area. In this report, by combining cylinder model with shell structure model, a new fingerprint was introduced to describe both the structural and physical-chemical features of the antigen and antibody protein. Furthermore, beside the description of individual protein, the specific epitope-paratope interaction fingerprint (EPIF) was developed to reflect the bond and the environment of the antigen-antibody interface. Finally, Proteochemometric Modeling of the antigen-antibody interaction was established and evaluated on 429 antigen-antibody complexes. By using only protein descriptors, our model achieved the best performance () among peers. Further, together with EPIF as a new cross-term, our model () can significantly outperform peers with multiplication of ligand and protein descriptors as a cross-term (). Results illustrated that: 1) our newly designed protein fingerprints and EPIF can better describe the antigen-antibody interaction; 2) EPIF is a better and specific cross-term in Proteochemometric Modeling for antigen-antibody interaction. The fingerprints designed in this study will provide assistance to the description of antigen-antibody binding, and in future, it may be valuable help for the high-throughput antibody screening. The algorithm is freely available on request. [ABSTRACT FROM AUTHOR]

Rocket based combined cycle (RBCC) engine is regarded as one of the most efficient propulsion systems for reusable space transportation vehicles and hypersonic cruise vehicles. It can perform excellently over a very broad range of Mach numbers and flight altitudes through multi-mode operations by effectively integrating high thrust-to-weight ratio of the rocket engine and high specific impulse of the airbreathing engine. The RBCC inlet, commonly operating in an extremely wide flight speed range covering static, subsonic, transonic, supersonic, and hypersonic, plays a vital role in the RBCC propulsion system and flight vehicles. This paper presents a comprehensive and systematical review of the research progress on the inlets for RBCC engines in different countries and different historical periods. A number of key technical and scientific issues specially concerning RBCC inlets are sorted out, including the wide range RBCC inlet design and optimization, inlet/embedded rocket/combustor matching and control, dynamic operation, etc. Several typical RBCC inlet applications and the corresponding research are discussed, including the Strutjet inlet, A5 inlet, GTX inlet, and the Astrox's inlet in the U.S., the RBCC inlet in JAXA, and a sidewall compression RBCC inlet in China. Finally, experience gained and some recommendations are summarized for future research of the RBCC inlet. [ABSTRACT FROM AUTHOR]