Entry Stage Research Articles

Simulation and accuracy analysis of orbit determination for TianQin using SLR data

TianQin project is a space gravitational wave detection project initiated by Sun Yat-sen University. It has high requirements for detectors’ orbit accuracy in the stages of orbit entry and scientific experiment operation. We obtain the different combinations of radial position errors and along-track velocity errors after analyzing the detectors orbit errors according to the stability requirements of TianQin constellation. Satellite laser ranging (SLR) is the space geodetic technique with the highest accuracy of range measurement, which is a commonly used method for satellite orbit determination. This paper uses solely simulated SLR data to determinate the precise orbit of TianQin detectors. We examine how the number of stations, the distribution of stations, and the measurement errors affect the SLR-only orbit determination accuracy. The results demonstrate that: (a) for the 7 days solution with 1 cm random errors and 0.5 cm systematic errors of SLR simulations, the average orbit determination accuracy of TianQin detectors is increasing from 27.37 m when using 5 Chinese stations to 9.34 m when using 6 Chinese stations. (b) The orbit determination accuracy can be significantly improved by optimizing the distribution of stations, which is increasing from 9.34 m for regional distribution to 1.75 m for global distribution when the number of stations is six. (c) When employing 6 Chinese stations, each 1 cm of random errors results in a deterioration in position accuracy by 19% and in velocity accuracy by 23%, each 1 cm of systematic errors affects 14% for position accuracy and 15% for velocity accuracy, respectively. While the impact of measurement errors on the orbit determination accuracy is aggravated when using 6 global distribution stations, which are 35% and 33% of 1 cm random errors and 17% and 20% of 1 cm systematic errors, respectively.

SARS-CoV-2 Inhibitors Identified by Phenotypic Analysis of a Collection of Viral RNA-Binding Molecules.

Antiviral agents are needed for the treatment of SARS-CoV-2 infections and to control other coronavirus outbreaks that may occur in the future. Here we report the identification and characterization of RNA-binding compounds that inhibit SARS-CoV-2 replication. The compounds were detected by screening a small library of antiviral compounds previously shown to bind HIV-1 or HCV RNA elements with a live-virus cellular assay detecting inhibition of SARS-CoV-2 replication. These experiments allowed detection of eight compounds with promising anti-SARS-CoV-2 activity in the sub-micromolar to micromolar range and wide selectivity indexes. Examination of the mechanism of action of three selected hit compounds excluded action on the entry or egress stages of the virus replication cycle and confirmed recognition by two of the molecules of conserved RNA elements of the SARS-CoV-2 genome, including the highly conserved S2m hairpin located in the 3'-untranslated region of the virus. While further studies are needed to clarify the mechanism of action responsible for antiviral activity, these results facilitate the discovery of RNA-targeted antivirals and provide new chemical scaffolds for developing therapeutic agents against coronaviruses.

Identification of an N-phenylsulfonyl-2-(piperazin-1-yl)methyl-benzonitrile derivative as Zika virus entry inhibitor

Zika virus (ZIKV) infection could cause severe neurological complications such as neonatal microcephaly, Guillain-Barré syndrome, and myelitis in adults. No vaccine or therapeutic drug is available for prevention and control of ZIKV infection yet. Based on previously reported anti-ZIKV hit compound 1, a series of novel N-benzoyl or phenylsulfonyl substituted 2-(piperazin-1-yl)methyl-benzonitrile (PMBN) derivatives was designed, synthesized, and investigated for the antiviral activity against ZIKV replication in different cell-based phenotypic assays. The results indicated that N-phenylsulfonyl-PMBN derivative 24 displayed the comparable antiviral activity and higher oral availability than hit compound 1. Meanwhile, mechanism of action study confirmed that compound 24 acts on the early entry stage of ZIKV life cycle. The identification of this new ZIKV entry inhibitor chemotype provided a promising lead for further optimization to develop new drug for ZIKV infection.

Measuring single-virus fusion kinetics using an assay for nucleic acid exposure

The kinetics by which individual enveloped viruses fuse with membranes provide an important window into viral-entry mechanisms. We have developed a real-time assay using fluorescent probes for single-virus genome exposure than can report on stages of viral entry including or subsequent to fusion pore formation and prior to viral genome trafficking. We accomplish this using oxazole yellow nucleic-acid-binding dyes, which can be encapsulated in the lumen of target membranes to permit specific detection of fusion events. Since increased fluorescence of the dye occurs only when it encounters viral genome via a fusion pore and binds, this assay excludes content leakage without fusion. Using this assay, we show that influenza virus fuses with liposomes of different sizes with indistinguishable kinetics by both testing liposomes extruded through pores of different radii and showing that the fusion kinetics of individual liposomes are uncorrelated with the size of the liposome. These results suggest that the starting curvature of such liposomes does not control the rate-limiting steps in influenza entry.

Shear thickening properties of nano SiO2/PEG dispersion system under impact loading

Shear thickening Fluid (STF) has a wide application in the field of protection due to its unique shear curing properties. However, the influences of particle content, constraint conditions, impact velocity and shear thickening properties of STF remain unclear. Therefore, SiO2 and PEG400 with a particle size of 100 nm were used as dispersoids and dispersants in the paper. The free drop of steel rod with different lengths have been conducted under the same speed and free boundary conditions. The dynamic mechanical behavior of the STF with fixed constraints at different speeds have been developed by using the Split Hopkinson Pressure Bar (SHPB). The experiment of free fall shows that the energy absorption of STF can be divided into three stages, namely, the entry stage, the equilibrium stage, and the recovery stage. During the entry stage, STF absorbs the external energy, and the equilibrium stage lasts about 3–4 ms. However when the mass fraction of dispersed in STF is 36%, the maximum loading distance of 400 mm steel bar is 1.4 mm at recovery stage. The SHPB experiment shows that the duration of the first response of STF is 20–25μs, and the wave velocity of STF is about 592.49 m/s.

Numerical investigation on drag characteristics of the truncated hemispherical-nose projectile in vertical water entry

ABSTRACT In this study, the feasibility of the ALE algorithm in analyzing the drag of a rigid truncated hemispherical-nose projectile at the initial stage of vertical water entry is examined. The water entry process is simulated under the conditions of different dilated half-angles of the head plane (DHAHPs) and muzzle velocities (u 0). The drag coefficient is obtained by dimensionless processing of the drag. The maximum (Cd max) drag coefficients of the initial stage are fitted to obtain the generalised impact laws of water entry. The results show that the larger the DHAHP, the smaller is u 0 and the higher is Cd max. The bivariate fitting formula for Cd max of the truncated hemispherical-nose projectile has high prediction accuracy and wide applicability. The average (Cd ave) drag coefficients of the projectile changes significantly after DHAHP of approximately 40°. This change is related to the wet state of the head.

Inhibition of KIF20A suppresses the replication of influenza A virus by inhibiting viral entry.

The influenza A virus (IAV) has caused several pandemics, and therefore there are many ongoing efforts to identify novel antiviral therapeutic strategies including vaccines and antiviral drugs. However, influenza viruses continuously undergo antigenic drift and shift, resulting in the emergence of mutated viruses. In turn, this decreases the efficiency of existing vaccines and antiviral drugs to control IAV infection. Therefore, this study sought to identify alternative therapeutic strategies targeting host cell factors rather than viruses to avoid infection by mutated viruses. Particularly, we investigated the role of KIF20A that is one of kinesin superfamily proteins in the replication of IAV. The KIF20A increased viral protein levels in IAV-infected cells by regulating the initial entry stage during viral infection. Furthermore, the KIF20A inhibitor significantly suppressed viral replication, which protected mice from morbidity and mortality. Therefore, our findings demonstrated that KIF20A is highly involved in the viral replication process and viral propagation both in vitro and in vivo, and could thus be used as a target for the development of novel antiviral drugs.

Strategic analysis on effects of technologies, government policies, and consumer perceptions on diffusion of hydrogen fuel cell vehicles

The market share of eco-friendly vehicles to minimize global greenhouse gas (GHG) emissions is still lower than that of ICEVs, especially the diffusion of hydrogen fuel cell vehicle (HFCV) being at the market entry stage. At present, the penetration rate of HFCV is below the government target, it is necessary to examine the effectiveness of related government policies. To this end, this study identified the factors affecting consumers preferences and diffusion of HFCV in South Korea and based on consumer preferences and expectation levels for the vehicle attribute, the future market share by the fuel type of vehicle was forecasted. Concretely, this study analyzed the stated-preference data using a discrete choice model which reflects the consumer theory, and predicted the future diffusion trend of HFCV, by considering development in related technologies and changes in government policies. The results revealed that an improvement in consumers' uncertainties about hydrogen has a more important impact on the diffusion of HFCVs than the expansion of charging infrastructure. Further, to achieve the HFCV supply target set by the South Korean government, it is necessary to raise positive awareness of HFCV along with lowering purchase price for HFCV and improvement in related technology levels.

Formulations of hydrodynamic force in the transition stage of the water entry of linear wedges with constant and varying speeds

The slamming and transition stages are the most important for the water entry of wedges, in which the wedges experience the main hydrodynamic forces. The slamming stage is fully investigated by analytical methods, while there are few formulations for the transition stage where the spray root exceeds the top of wedge. Motivated by that, this paper numerically studies the transition stage of the water entry of linear wedges with constant and varying speeds, with assumptions that the fluid is incompressible, inviscid and with negligible effects of gravity and surface tension, and the flow is irrotational. For the constant speed impact, the similitude of the declining forces between different deadrise angles in the transition stage is found by scaling the differences between the maximum values in the slamming stage and the results of steady supercavitating flow. The hydrodynamic force is formulated based on the similitude of the declining forces in the transition stage together with the linear increasing forces in the slamming stage. For the varying speed impact, the hydrodynamic force component caused by the acceleration effect in the transition stage is formulated by an added mass coefficient with an average increase of 27.13% compared with that of slamming stage. Finally, a general expression of the hydrodynamic forces in both the slamming and transition stages is thus proposed and has good predictions in the range of deadrise angles from 5° to 70° for both the constant and varying speed impacts.

Numerical Study on Dynamic Characteristics of Vehicle Entering Water at High Speed

Aiming at a design for buffering and load reduction configuration for a large-scale (diameter greater than 500 mm) vehicle entering water at high speed (greater than 100 m/s), a numerical model for a vehicle entering water at high speed was employed based on an arbitrary Lagrange-Euler (ALE) algorithm. Combined with modal analysis and shock response spectrum, the influence of the head cap on the dynamic characteristics of the structure was analyzed. The results showed that the peak value and pulse width of the impact load on the vehicle increased with the increase in the speed of water entry. The existence of the head cap increased the complexity of the forces on the vehicle during the process of water entry. The initial formation of the cavity was greatly affected by the head cap. The head cap and the vehicle separated in the later stage of the water entry. During the process of water entry, the shell of the vehicle was mainly compressed and bent and the head cap reduced the deformation. The relevant conclusions of this paper can provide some input for the design of a new buffering structure and vehicle shell.

Virus-Like Particles of SARS-CoV-2 as Virus Surrogates: Morphology, Immunogenicity, and Internalization in Neuronal Cells.

The engineering of virus-like particles (VLPs) is a viable strategy for the development of vaccines and for the identification of therapeutic targets without using live viruses. Here, we report the generation and characterization of quadruple-antigen SARS-CoV-2 VLPs. VLPs were generated by transient transfection of two expression cassettes in adherent HEK293T cells—one cassette containing Mpro for processing of three structural proteins (M, E, and N), and the second cassette expressing the Spike protein. Further characterization revealed that the VLPs retain close morphological and antigenic similarity with the native virus and also bind strongly to the SARS-CoV-2 receptor hACE-2 in an in vitro binding assay. Interestingly, the VLPs were found to internalize into U87-MG cells through cholesterol-rich domains in a dynamin-dependent process. Finally, our results showed that mice immunized with VLPs induce robust humoral and cellular immune responses mediated by enhanced levels of IL-4, IL-17, and IFNγ. Taken together, our results demonstrate that VLPs mimic the native virus and induce a strong immune response, indicating the possible use of these particles as an alternative vaccine candidate against SARS-CoV-2. VLPs can also be effective in mapping the initial stages of virus entry and screening inhibitors.

Effects and mechanism of Aβ1−42 on EV-A71 replication

Backgroundβ-Amyloid (Aβ) protein is a pivotal pathogenetic factor in Alzheimer’s disease (AD). However, increasing evidence suggests that the brain has to continuously produce excessive Aβ to efficaciously prevent pathogenic micro-organism infections, which induces and accelerates the disease process of AD. Meanwhile, Aβ exhibits activity against herpes simplex virus type 1 (HSV-1) and influenza A virus (IAV) replication, but not against other neurotropic viruses. Enterovirus A71 (EV-A71) is the most important neurotropic enterovirus in the post-polio era. Given the limitation of existing research on the relationship between Aβ and other virus infections, this study aimed to investigate the potent activity of Aβ on EV-A71 infection and extended the potential function of Aβ in other unenveloped viruses may be linked to Alzheimer's disease or infectious neurological diseases.MethodsAβ peptides 1–42 are a major pathological factor of senile plaques in Alzheimer’s disease (AD). Thus, we utilized Aβ1–42 as a test subject to perform our study. The production of monomer Aβ1–42 and their high-molecular oligomer accumulations in neural cells were detected by immunofluorescence assay, ELISA, or Western blot assay. The inhibitory activity of Aβ1–42 peptides against EV-A71 in vitro was detected by Western blot analysis or qRT-PCR. The mechanism of Aβ1–42 against EV-A71 replication was analyzed by time-of-addition assay, attachment inhibition assay, pre-attachment inhibition analysis, viral-penetration inhibition assay, TEM analysis of virus agglutination, and pull-down assay.ResultsWe found that EV-A71 infection induced Aβ production and accumulation in SH-SY5Y cells. We also revealed for the first time that Aβ1–42 efficiently inhibited the RNA level of EV-A71 VP1, and the protein levels of VP1, VP2, and nonstructural protein 3AB in SH-SY5Y, Vero, and human rhabdomyosarcoma (RD) cells. Mechanistically, we demonstrated that Aβ1–42 primarily targeted the early stage of EV-A71 entry to inhibit virus replication by binding virus capsid protein VP1 or scavenger receptor class B member 2. Moreover, Aβ1–42 formed non-enveloped EV-A71 particle aggregates within a certain period and bound to the capsid protein VP1, which partially caused Aβ1–42 to prevent viruses from infecting cells.ConclusionsOur findings unveiled that Aβ1–42 effectively inhibited nonenveloped EV-A71 by targeting the early phase of an EV-A71 life cycle, thereby extending the potential function of Aβ in other non-envelope viruses linked to infectious neurological diseases.

Simulation of water entry into shallow water based on boundary element method

The problem of a two-dimensional wedge entering into shallow water is investigated with the boundary element method based on the potential flow theory, and fully nonlinear boundary conditions in time domain are imposed. A stretched coordinate system is used at the initial stage of water entry to avoid the numerical problems originated from extremely small wetted surface. An auxiliary function is used to calculate the pressure on the body surface. The free surface is updated through the fourth order Runge-Kutta scheme. Particularly, a jet cut model is used to avoid the numerical difficulties when the thin and high jet forms. Detailed results through the free surface, pressure distribution and hydrodynamic load at constant speed and prescribed time-varying speed are provided, the comparison with the results from experiments, Wagner theory, semi-analytic method are made and effects of water depth are investigated in detail. It is found that the bottom of the shallow water domain would exert a noticeable effect on the pressure distribution and force of the wedge, especially when the tip of wedge is close to the domain bottom.

Surfing the tide: Homeward migration of sea trout (Salmo trutta) in a Patagonian river

This study evaluates the influence of marine and freshwater conditions on the timing of river entry and upstream migration of sea trout (Salmo trutta) in the Grande River of Tierra del Fuego, Patagonia. We analysed the in-river catch-and-release records from a group of fishing lodges that dominate the Grande River fishery during January-April 2008 (n=5029 fish) as a function of environmental variables: tidal amplitude, stage in the lunar cycle, river discharge, and river water temperature along the homeward migration season. We discuss the value of the daily catch rate as an abundance index in the Grande river, then analyse the temporal structure of the tidal cycle in the Grande River estuary, a macro-tidal environment with a mean tidal amplitude of 5.7m, and analyse the fit of a generalized additive model to trout catches on a daily basis in four sections along the river to identify the environmental variables that may affect trout abundance throughout the homeward migration. Fish catches in each section of the river were differentially affected by specific environmental variables: tidal amplitude had a positive and significant effect on catches in the lower river sections, whereas water temperature and river discharge significantly affected catches in upper sections (positive effect of temperature; negative effect of discharge). Catches in the lower section clearly reflect the river entry stage of the homeward migration, with a bi-modal shape significantly correlated with the tidal cycle. The first peak was composed mainly of larger multi-sea-winter trout that move upstream, whereas the second one had a wider range of fish lengths, including a large proportion of small and maybe nonreproductive trout that overwinter in the lower river. Based on our results, we conclude that the large tides in the Grande River estuary strongly affect the river entry timing of sea trout. The underlying mechanisms of this effect may be a combination of increased olfactory recognition and increased tidal transport modulated by the seasonal tidal cycle, which operates on trout during coastal migration to produce the pulses observed in the Grande River sea trout run. In the middle and upper sections of the river, where the tidal effect at river entry was dissipated as upstream migration progressed, trout catches increased with water temperature and decreased with river discharge, which may operate through their influence on in-river migration rate and abundance, but also through changes in catchability.

How Do Latecomers Catch Up Fast in CoPS? A Study of CIMC in Marine Equipment Manufacturing Industry

Catching up in Complex Product Systems (CoPS) requires systematic integration from several advanced technological fields and usually demands a strong reputation based on an existing record of success in project delivery. It thus makes entry and capability development extremely challenging for latecomers. Through a longitudinal, exploratory case study spanning 13 years, this study investigates how firms that lack prior experience in developing CoPS can survive and catch up fast. It finds that latecomer firms can adopt the synergy strategy to address multiple problems collectively over time and thus achieve rapid catch-up. In the entry stage, latecomers implement the resource-synergy strategy to overcome great market risk and latecomer disadvantages, realizing capability legitimizing for survival. In the gradual catch-up stage, driven by the needs of strategic transformation, latecomers utilize the routine-synergy strategy for capability structuring and thus enhance their market position and technological know-how. In the leapfrogging stage, to seize innovative opportunities in the sectoral system, latecomers carry out the value-synergy strategy and thus improve capability dynamics required for sustaining industrial leadership. The occurrence of the rapid catch-up process is mainly attributed to firms’ acute awareness, strong motivation, and asymmetric capability. Our study offers a process framework that shows how latecomer firms realize fast catch-up in CoPS sectors, providing managerial implications for other emerging economies to overcome high barriers to entry and then to build the capabilities that are required for developing CoPS.

Estimating New Cases Among Athletes During the Winter Olympics Based on a Dynamic Model - Beijing, China, February 2022.

IntroductionSince first appearing in late 2021, the Omicron variant has spread rapidly around the world. Nevertheless, the XXIV Winter Olympic Games (WOG) were held in Beijing in February 2022, which undoubtedly posed a huge challenge to domestic epidemic prevention and control.MethodsTo analyze and evaluate the spread of the epidemic within the closed-loop management of the Beijing 2022 WOG, an improved dynamics model was established. Using the known dynamics parameters, the new daily cases and final members of quarantined people were predicted, and the influence of different factors on the change of the number of quarantined people was analyzed.ResultsWhen the proportion of exposed persons being detected and the degree of admixture between the two populations varied between 0.5 and 0.9, there was little change in the daily predicted number of new cases and the final number of quarantined patients. As the initial value of the exposed among inbound personnel increased, the final size of quarantined patients increased proportionally.DiscussionFrom the analysis results, detecting potential virus carriers at the entry stage is the most effective way to control the spread of the epidemic within the closed-loop management of the Beijing 2022 WOG.

Recycling Strategies for Solid Oxide Cells

AbstractAlongside the generation of renewable power and its storage in batteries, hydrogen technologies are essential to enable a deep decarbonization of the energy system. These technologies include solid oxide cells (SOCs), which can be operated as electrolyzers to generate hydrogen or syngas and/or for power supply in fuel cell mode and demonstrate the highest electrical efficiency among electrochemical converters. However, SOCs like other energy technologies contain significant amounts of critical raw materials, which should be preserved appropriately. Therefore, the development of economically viable recycling strategies is required even at an early market entry stage. In this paper, potential recycling routes for SOC stack components are discussed. Based on state‐of‐the‐art materials and cell designs, the future challenges related to SOC recycling are outlined, and possible recycling pathways for all SOC components are presented with an emphasis on the ceramic fractions. Their economic and environmental potentials are evaluated, showing the significant advantages offered by recycling.

Exploration of Mathematics Problem Solving Processes of Junior High School Students with Different Levels of Logical Thinking Ability

Problem solving is one of the most important skills for students. Meanwhile, logical thinking is the ability to solve problems by relying on mental abilities. The purpose of this research is to describe the problem solving process of students with different levels of logical thinking. This research is an exploratory qualitative research involving eighth grade students of SMP N 5 Tuban who have different levels of logical thinking as research subjects. The subjects who were interviewed were 4 students. Instruments to measure the level of logical thinking used The Group Assessment of Logical Thinking (GALT) while exploring the process of solving problems using the stages of entry, attack, and review. The results of the analysis show that students with high logical thinking skills meet the entry, attack, and review stage. Students with low logical thinking skills meet the entry stage in ‘know’ and ‘want’ aspects only, at the attack stage they only meet the try and possible aspects, and do not meet the review stage at all. Thus, it can be concluded that students with different levels of logical thinking ability have different mathematical problem solving abilities.

Do Employees Work Less for Female Leaders? A Multi-Method Study of Entrepreneurial Firms

We propose that female-founded ventures receive a lower amount of employee labor for equal pay because employees are more likely to decline requests for additional labor by female founders. First, using longitudinal matched employer-employee data covering all founders of new ventures with personnel in Portugal between 2002 and 2012, we confirm that full-time employees contribute fewer regular hours and less overtime work to female-founded firms. Second, using a series of online experiments, we show that this variation in employee labor across female and male-founded firms is partly motivated by a difference in the employee’s expectations of work demands. Specifically, employees perceive female founders’ requests for additional labor to be unfair and more difficult than expected, and both these perceptions explain the lower amount of employee labor supplied in female-founded ventures. Overall, our findings uncover a novel mechanism that helps explain the existence of a gender gap in entrepreneurship beyond the entry stage. Supplemental Material: The online appendices are available at https://doi.org/10.1287/orsc.2022.1611 .

Socialization at Universities: A Case Study

Socialization process has a significant impact on learning, which is a basic requirement for both the organization and the role performance of the newcomer to the organization. It is considered very important for a new member to socialize organizationally and professionally. This paper focuses on revealing the process of organizational and professional socialization of academicians. In accordance with this purpose, in-depth interviews were conducted with 14 research assistants from various fields as representative of the academician group. The data obtained from the interviews were analyzed by content analysis method and some conceptual determinations were generated. According to the findings, almost all the academicians did not encounter any practice or socialization tool that would make them feel belonging to the profession and the organization or that would ensure their harmony with the institution they were in. The participants, who stated that they try to learn both the requirements of the profession and the problems they encounter in the organization mostly by their own individual efforts, stated that they achieved satisfaction far below their expectations, especially at the entry stage. As a result, it has been revealed that academicians are mostly alone in the process of learning academic life from the pre-entry stage to the settlement stage. It is necessary to establish certain programs at each university in order to socialize research assistants, who are in the first phase of the path to becoming faculty members, both in the organizational and professional context. It is further recommended that activities should be organized that will provide the following: direct assistance for time management, understanding scientific/academic processes, and learning organizational norms and values.