133 research outputs found
Abundance ratios of OH/CO and HCO+/CO as probes of the cosmic ray ionization rate in diffuse clouds
The cosmic-ray ionization rate (CRIR, ) is one of the key parameters
controlling the formation and destruction of various molecules in molecular
clouds. However, the current most commonly used CRIR tracers, such as H,
OH, and HO, are hard to detect and require the presence of
background massive stars for absorption measurements. In this work, we propose
an alternative method to infer the CRIR in diffuse clouds using the abundance
ratios of OH/CO and HCO/CO. We have analyzed the response of chemical
abundances of CO, OH, and HCO on various environmental parameters of the
interstellar medium in diffuse clouds and found that their abundances are
proportional to . Our analytic expressions give an excellent
calculation of the abundance of OH for 10 s,
which are potentially useful for modelling chemistry in hydrodynamical
simulations. The abundances of OH and HCO were found to monotonically
decrease with increasing density, while the CO abundance shows the opposite
trend. With high-sensitivity absorption transitions of both CO (1--0) and
(2--1) lines from ALMA, we have derived the H number densities () toward 4 line-of-sights (LOSs); assuming a kinetic temperature of
, we find a range of
(0.140.03--1.20.1)10 cm}. By comparing the
observed and modelled HCO/CO ratios, we find that in our diffuse
gas sample is in the { range of 10 10 s. This is 2 times higher
than the average value measured at higher extinction, supporting an attenuation
of CRs as suggested by theoretical models.Comment: 22 pages, 9 figures, accepted by Ap
Haemodynamic mechanism of formation and distribution of coronary atherosclerosis: A lesion-specific model
© IMechE 2020. Coronary arterial disease, as the most devastated cardiovascular disease, is caused by the atherosclerosis in the coronary arteries, which blocks the blood flow to the heart, resulting in the deficient supply of oxygen and nutrition to the heart, and eventually leading to heart failure. To date, haemodynamic mechanisms for atherosclerosis development are not fully understood although it is believed that the haemodynamic disturbance at the region of the arterial bifurcation, particular, bifurcation angle, plays an important role in the atherosclerosis development. In this study, two types of computational fluid dynamics models, lesion-specific and idealized models, combined with the computer tomography imaging techniques, are used to explore the mechanism of formation and distribution of the atherosclerosis around the bifurcation of left coronary artery and its association with the bifurcation angle. The lesion-specific model is used to characterize the effect of personalized features on the haemodynamic performance, while the idealized model is focusing on the effect of single factor, bifurcation angle, on the haemodynamic performance. The simulated results from both types of the models, combined with the clinical observation, revealed that the three key areas around the bifurcations are prone to formation of the atherosclerosis. Unlike the idealized models, lesion-specific modelling results did not show the significant correlation between the wall shear stress and bifurcation angle, although the mean value of the wall shear stress in smaller bifurcation angles (less than 90°) is higher than that with larger bifurcation angles (greater than 90°). In conclusion, lesion-specific computational fluid dynamics modelling is an efficient and convenient way to predict the haemodynamic performance around the bifurcation region, allowing the comprehensive information for the clinicians to predict the atherosclerosis development. The idealized models, which only focus on single parameter, may not provide the sufficient and reliable information for the clinical application. A novel multi-parameters modelling technique, therefore, is suggested to be developed in future, allowing the effects of many parameters on the haemodynamic performance to be evaluated
Dependence of Chemical Abundance on the Cosmic Ray Ionization Rate in IC 348
Ions (e.g., H, HO) have been used extensively to quantify the
cosmic-ray ionization rate (CRIR) in diffuse sightlines. However, measurements
of CRIR in low-to-intermediate density gas environments are rare, especially
when background stars are absent. In this work, we combine molecular line
observations of CO, OH, CH, and HCO in the star-forming cloud IC~348, and
chemical models to constrain the value of CRIR and study the response of the
chemical abundances distribution. The cloud boundary is found to have an
of approximately 4 mag. From the interior to the exterior of the
cloud, the observed CO line intensities drop by an order of magnitude.
The calculated average abundance of CO (assuming C/C = 65)
is (1.20.9) 10, which increases by a factor of 6 from the
interior to the outside regions. The average abundance of CH (3.30.7
10) is in good agreement with previous findings in diffuse and
translucent clouds ( 5 mag). However, we did not find a decline
in CH abundance in regions of high extinction (8 mag) as
previously reported in Taurus. By comparing the observed molecular abundances
and chemical models, we find a decreasing trend of CRIR as
increases. The inferred CRIR of = (4.71.5)
10 s at low is consistent with H measurements
toward two nearby massive stars.Comment: 21 pages, 11 figures. Submitted to Ap
Analysis between ABO blood group and clinical outcomes in COVID-19 patients and the potential mediating role of ACE2
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become the most common coronavirus that causes large-scale infections worldwide. Currently, several studies have shown that the ABO blood group is associated with coronavirus disease 2019 (COVID-19) infection and some studies have also suggested that the infection of COVID-19 may be closely related to the interaction between angiotensin-converting enzyme 2 (ACE2) and blood group antigens. However, the relationship between blood type to clinical outcome in critically ill patients and the mechanism of action is still unclear. The current study aimed to examine the correlation between blood type distribution and SARS-CoV-2 infection, progression, and prognosis in patients with COVID-19 and the potential mediating role of ACE2. With 234 patients from 5 medical centers and two established cohorts, 137 for the mild cohort and 97 for the critically ill cohort, we found that the blood type A population was more sensitive to SARS-CoV-2, while the blood type distribution was not relevant to acute respiratory distress syndrome (ARDS), acute kidney injury (AKI), and mortality in COVID-19 patients. Further study showed that the serum ACE2 protein level of healthy people with type A was significantly higher than that of other blood groups, and type O was the lowest. The experimental results of spike protein binding to red blood cells also showed that the binding rate of people with type A was the highest, and that of people with type O was the lowest. Our finding indicated that blood type A may be the biological marker for susceptibility to SARS-CoV-2 infection and may be associated with potential mediating of ACE2, but irrelevant to the clinical outcomes including ARDS, AKI, and death. These findings can provide new ideas for clinical diagnosis, treatment, and prevention of COVID-19
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