Analysis of Longitudinal Guided Wave Propagation in a Liquid-Filled Pipe Embedded in Porous Medium

To study the leakage situation of a liquid-filled pipe in long-term service, a model of a liquid-filled pipe embedded in an infinite porous medium as well as in a finite porous medium is designed. The principal motivation is to perform detailed quantitative analysis of the longitudinal guided wave propagating in a liquid-filled pipe embedded in a saturated porous medium. The problems of pipeline leakage and porosity as well as the media outside the pipe are solved to identify the characteristics of the guided wave in a more practical model. The characteristics of the guided wave are investigated theoretically and numerically, with special emphasis on the influence of porous medium parameters on the dispersion properties. Assuming the pipe is a cylindrical shell buried in an isotropic, homogeneous, and porous medium, the dispersion equations are established based on the elastic-dynamic equations and the modified Biot liquid-saturated porous theory. The characteristics of dispersion, time-domain waveform and attenuation curves varying with porous medium parameters, wrapping layer material, and thickness, are all analyzed. The increase in porosity decreases the partial mode phase velocity in the liquid-filled pipe embedded in the finite porous medium. The characteristics of attenuation are in good agreement with the dispersion curves and the time-domain waveform results.

Mechanistic Insights to the Binding of Antibody CR3022 Against RBD from SARS-CoV and HCoV-19/SARS-CoV-2: A Computational Study

Aims & Objective: Corona Virus Disease 2019 (COVID-19) caused by the human coronavirus 2019 (HCoV-19, also known as SARS-CoV-2) infection is currently in a global outbreak. COVID-19 has posed a huge threat to public health and economic stability worldwide. CR3022, a human monoclonal neutralizing antibody isolated from a Severe Acute Respiratory Syndrome (SARS) recovery patient, was confirmed to be able to bind the S protein of HCoV-19 with a certain degree of neutralizing activity. Crystal structural information indicated that CR3022 could bind to the epitope on the receptor binding domain (RBD) of HCoV-19, whose epitope consists of 28 amino acids, and 24 of them are conserved in SARS-CoV of SARS. However, the crystal structure is only a static conformation at a certain moment in time, and it cannot provide dynamic details of the interaction between antigen and antibody. Methods: In this study, molecular dynamics (MD) simulation combined with MM/PBSA and CAS methods were performed to investigate the binding mechanism of binding of CR3022 against SARS-CoV-RBD and HCoV-19-RBD in order to determine their holographic dynamic information. Results: It was found that the CR3022-SARS-CoV-RBD complex was more stable during 100ns MD run than that of the CR3022-HCoV19-RBD system. There were common conservative amino acids on the β2 sheet of RBD, including Tyr369, Phe377, Lys378, Tyr380, Gly381, Lys386, Leu390 and others. These conservative amino acids play significant roles in the binding process of CR3022 antibody against SARS-CoV-RBD and HCoV-19-RBD. It was also found that the binding mode of CR3022 to its native target SARS-CoV-RBD is more comprehensive and uniform. Moreover, the β2 sheet residue Thr385 and non-β2 sheet residues Arg408 and Asp428 of the CR3022- SARS-CoV-RBD system were found to be crucial for their binding affinities, thus forming a special conformational epitope. However, these key amino acids are not present in the CR3022-HCoV-19-RBD system. The binding mode of CR3022 and HCoV-19-RBD is similar to that of SARS-CoV-RBD, but the deficiency of crucial hydrogen-bonds and salt-bridges. Therefore, the binding of CR3022 and HCoV19-RBD only draws on the partial mode of the binding of CR3022 and SARS-CoV-RBD, so there is a loss of affinity. Conclusion: Thus, in order to better fight the epidemic of COVID-19 with the CR3022 antibody, this antibody needs to further improve the neutralization efficiency of HCoV-19 through mutation of it’s CDR region.

New observations and asteroseismic analysis of the subdwarf B pulsator PG 1219+534

We present a new asteroseismic modeling of the hot B subdwarf (sdB) pulsator PG 1219+534, based on a 3- month campaign with the Mont4K/Kuiper combination at Mt Bigelow (Arizona) and on updated atmospheric parameters from high S/N low and medium resolution spectroscopy. On the basis of the nine independent pulsation periods extracted from the photometric light curve, we carried out an astroseismic analysis by applying the forward modeling approach using our latest (third and fourth generation) sdB models. Atmospheric parameters (Teff = 34 258 ± 170 K, log g = 5.838 ± 0.030) were used as independent constraints, as well as partial mode identification based on observed multiplet structures we ascribed to stellar rotation. The optimal model found is remarkably consistent between various analyses with third and fourth generation of sdB models, and also with previously published analysis with second generation sdB models. It corresponds to a sdB with a canonical mass (0.46 ± 0.02 M⊙), rather thin H-He envelope (log q(envl) = −3.75 ± 0.12), and close to He-burning exhaustion (Xcore(C + O) = 0.86 ± 0.05).We also investigate the internal rotation of the star.We find that PG 1219+534 rotates very slowly (Prot = 34.91 ± 0.84 days) and that solid-body rotation is reached at least down to ∼60% of the radius.

Prevalence and Prognosis Impact of Patient–Ventilator Asynchrony in Early Phase of Weaning according to Two Detection Methods

Background Patient–ventilator asynchrony is associated with a poorer outcome. The prevalence and severity of asynchrony during the early phase of weaning has never been specifically described. The authors’ first aim was to evaluate the prognosis impact and the factors associated with asynchrony. Their second aim was to compare the prevalence of asynchrony according to two methods of detection: a visual inspection of signals and a computerized method integrating electromyographic activity of the diaphragm. Methods This was an ancillary study of a multicenter, randomized controlled trial comparing neurally adjusted ventilatory assist to pressure support ventilation. Asynchrony was quantified at 12, 24, 36, and 48 h after switching from controlled ventilation to a partial mode of ventilatory assistance according to the two methods. An asynchrony index greater than or equal to 10% defined severe asynchrony. Results A total of 103 patients ventilated for a median duration of 5 days (interquartile range, 3 to 9 days) were included. Whatever the method used for quantification, severe patient–ventilator asynchrony was not associated with an alteration of the outcome. No factor was associated with severe asynchrony. The prevalence of asynchrony was significantly lower when the quantification was based on flow and pressure than when it was based on the electromyographic activity of the diaphragm at 0.3 min–1 (interquartile range, 0.2 to 0.8 min–1) and 4.7 min–1 (interquartile range, 3.2 to 7.7 min–1; P < 0.0001), respectively. Conclusions During the early phase of weaning in patients receiving a partial ventilatory mode, severe patient–ventilator asynchrony was not associated with adverse clinical outcome, although the prevalence of patient–ventilator asynchrony varies according to the definitions and methods used for detection.