Molecular dynamics study of the frictional properties of multilayer MoS2

To reveal the friction mechanism of molybdenum disulfide (MoS₂), the frictional properties of multilayer MoS₂ lubrication film were studied under variable loads and shearing velocities by the molecular dynamics (MD) method. The results showed irreversible deformation of MoS₂ was caused by heavy load or high shear velocity during the friction process and the interlayer velocity changed from a linear to a ladder-like distribution; thus, the number of shear surfaces and the friction coefficient decreased. The low friction coefficient caused by heavy load or high velocity could be maintained with a decrease in load or velocity. For a solid MoS₂ lubrication film, the number of shearing surfaces should be reduced as much as possible and the friction pair should be run under heavy load or high shear velocity for a period of time in advance; thus, it could exhibit excellent frictional properties under other conditions. The proposed friction mechanism provided theoretical guidance for experiments to further improve the frictional properties of MoS₂.

Deformation of MoS₂ layers directly leads to decrease in potential and ultimately leads to decrease in friction coefficient.     

The preparation and characterization of a carbon fiber-reinforced epoxy resin and EPDM composite using the co-curing method

Due to the development of the aerospace technology, the requirements for composite materials have become stricter. Thus, in this work, a completely novel technology, which has not been reported elsewhere, was used to prepare a composite of a carbon fiber-reinforced epoxy resin (CFRP) and ethylene-propylene-diene rubber (EPDM), which was denoted as CFRP/EPDM; CFRP and EPDM are commonly used as a shell and heat insulation layer, respectively, in the solid rocket industry. The composite system had good adhesive ability, as confirmed by the 90° peel strength test, even though the EPDM rubber is non-polar in nature. Additionally, the adhesive mechanism between CFRP and EPDM was determined using scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) indicated that the T_d10% value of the CFRP/EDPM composite was slightly higher than that of CFRP. According to the nuclear magnetic resonance (NMR) spectroscopy results of the EPDM rubber and the interlaminar shear strength (ILSS) of CFRP, we can conclude that the co-curing method will not damage the properties of CFRP and EPDM.

The CFRP/EPDM composite was prepared by a one-step co-curing method, which was very convenient and energy effective.     

One-step synthesis of hydrophobic clinoptilolite modified by silanization for the degradation of crystal violet dye in aqueous solution

Hydrophobic clinoptilolite (CP) was successfully synthesized via a silanization method using methyltriethoxysilane (MTS) or diethoxydimethylsilane (DMTS) as silane coupling agents. The structural and textural properties of the resultant hydrophobic CP were characterized using various methods. The effect of the amount of MTS or DMTS additive on the induction (nucleation) and growth of CP were also investigated, and the apparent activation energy values for induction and growth periods were calculated, suggesting that the induction period is kinetically controlled, while the rapid growth process is thermodynamically controlled. Meanwhile, DMTS modification enhanced the hydrophobicity of CP compared with its MTS-modified counterpart and pure CP. Finally, various ZnO-supported CPs were used as photocatalysts for the removal of crystal violet from aqueous solution, demonstrating that ZnO/hydrophobic CP has the largest adsorption capacity and best removal performance. These results suggest that hydrophobic CP, as an adsorbent or support, has the most potential for applications in separation and catalysis.

One-step synthesis of hydrophobic CPs was demonstrated, in which the kinetically-controlled induction period and thermodynamically-based rapid growth process were elucidated.     

Factors Associated with Compliance to the Hospital Price Transparency Final Rule: a National Landscape Study

BACKGROUNDThe Hospital Price Transparency Final Rule, effective January 1, 2021, requires hospitals to post online a machine-readable file that includes payer-specific negotiated commercial prices for all services. The regulation aims to improve the affordability of hospital care by promoting price competition. However, a low compliance level among hospitals would compromise the operational effectiveness of this regulation. Understanding hospitals’ compliance status to the regulation has important implications for its enforcement effort and effectiveness assessment.OBJECTIVETo analyze nationwide hospitals’ compliance status to the Hospital Price Transparency Rule.DESIGNCross-sectional observational study.PARTICIPANTSA total of 3558 Medicare-certified general acute-care hospitals were examined.MAIN MEASURESA binary compliance rating was generated by using data collected by Turquoise Health. “Noncompliance” means that no machine-readable file was posted or the posted file contains no commercial negotiated prices. “Compliance” means that a machine-readable file was posted with commercial negotiated prices for at least one insurance plan.KEY RESULTSAs of June 1, 2021, 55% of the 3558 Medicare-certified general acute-care hospitals we examined had not posted a machine-readable file containing commercial negotiated prices. Wide variations of compliance existed across states and hospital referral regions. A hospital’s compliance status is strongly associated with the average compliance status of peer hospitals in the same market. Hospitals with greater IT preparedness, for-profit hospitals, system-affiliated hospitals, large hospitals, and non-urban hospitals had greater compliance. More concentrated hospital markets had greater average compliance.CONCLUSIONSHospitals take into consideration the behavior of their peers in the same market when making price disclosure decisions. Compliant hospitals are likely to have better IT preparedness, more financial resources and personnel expertise to mitigate the cost required for the implementation of the Price Transparency Rule. The compliance cost, therefore, might be a barrier for some hospitals.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11606-021-07237-y.     

Influence of Solvent-Dependent Morphology on Molecular Doping and Charge Transport in Conductive Thiophene Polymer

The utility of a solvent is one of the key factors that impacts resultant film morphology. However, the effect of solvent-dependent morphology on the doping process and electrical conductivity has not been adequately elucidated. In this work, we compared the morphology of chloroform- and chlorobenzene-processed thiophene polymer films and investigated how the choice of solvent influences film morphology, doping level, charge transport properties, and thus electrical conductivity. It was found that the film drop-casted from chloroform exhibits better crystallinity than that drop-casted from chlorobenzene. The crystallinity has negligible impact on the doping level but significant impact on charge transport properties. As a result, the chloroform-processed film shows a higher electrical conductivity of up to 408 S cm⁻¹ due to a high carrier mobility related to the continuously crystalline domains in film. This finding indicates that the choice of solvent for preparation of film, which strongly correlated with molecular orientation, is a new strategy to optimize the electrical conductivity of doped polymers.     

Associations of blood pressure components with risks of cardiovascular events and all‐cause death in a Chinese population: A Prospective Study

The associations of blood pressure components with cardiovascular risks and death remain unclear, and the definition of wide pulse pressure (PP) is still controversial. Using data from 1257 participants without a history of cardiovascular disease, who were followed for 4.84 years, we performed multivariable Cox regression analyses to assess how systolic blood pressure (SBP), diastolic blood pressure (DBP), and PP contribute to risks of cardiovascular events and all‐cause death. Among all participants, SBP and PP were significantly associated with the risks of cardiovascular events and all‐cause death (all p < .05). DBP was not significantly associated with the risk of all‐cause death; rather, it was only associated with a marginally significant 1% increased risk for cardiovascular events (p = 0.051). In participants aged < 65 years, DBP was significantly associated with a 3% increased risk for cardiovascular events (hazard ratio [HR]: 1.03, 95% confidence interval [95% CI]: 1.01–1.06). The association between PP and cardiovascular events appeared to be J‐shaped in comparison to participants with the lowest‐risk PP (50–60 mmHg), with adjusted HRs of 1.71 (95% CI: 1.03–2.85), 1.63 (95% CI: 1.00–2.68), and 2.13 (95% CI: 1.32–3.43) in the <50, 60.0–72.5, and ≥72.5 mmHg subgroups, respectively. The optimal cutoff points of a wide PP for predicting the risks of cardiovascular events and all‐cause death were 70.25 and 76.25 mmHg, respectively. SBP and PP had a greater effect on cardiovascular risk, whereas DBP independently influenced cardiovascular events in middle‐aged participants. Considerable PP alterations should be avoided in antihypertensive treatment.     

Experimental Investigation on Mechanical Properties of Geocell Strips at Low Temperature

Geocell is widely used in the treatment of poor roadbed, which can restrain soil laterally and improve the stability of soil. In cold area engineering, a change in temperature can influence the mechanical properties of geocell of different materials. To study the mechanical response of geocell at low temperatures, three types of geocell strips commonly used in engineering, namely the polyethylene (HDPE), polypropylene (PP), and polyester (PET), were studied via the uniaxial tensile test at the ambient temperatures of −5 °C, −20 °C, and −35 °C, respectively. Meanwhile, the tensile strength, fracture mode, and temperature sensitivity of geocell specimens were compared. It is concluded that: (1) at low temperatures, the tensile strengths of HDPE and PET geocell strips are significantly improved, while that of the PP geocell strip is less sensitive to the temperature. (2) The PP geocell is subject to a brittle failure at all ambient temperatures. The PET geocell strip experiences a hard-ductile failure at normal temperatures of −5 °C and −20 °C. While in the tensile test at −35 °C, it is prone to brittle failure and hard-ductile failure. The HDPE geocell strip suffers from ductile failure at all ambient temperatures. (3) At low temperatures, overall, the tensile properties of the PET geocell strip is better than those of the PP and HDPE geocell strips.     

Effect of continuous hemofiltration on hemodynamics, lung inflammation and pulmonary edema in a canine model of acute lung injury

Objective This study examined whether continuous hemofiltration favorably affects cardiopulmonary variables, lung inflammation, and lung fluid balance in a canine model of oleic acid induced acute lung injury.Methods Eleven pentobarbital-anesthetized dogs were randomly divided into a control (mechanical ventilation, MV) group (n=6) and a MV plus hemofiltration (HF) group (n=5). All animals received an intravenous injection of oleic acid (0.09 ml/kg) to induce acute lung injury. Continuous arterial-venous hemofiltration (blood flow 100 ml/min, ultrafiltration rate at 50–65 ml kg^–1 h^–1) was started after establishment of oleic acid induced acute lung injury and continued for 4 h. Hemodynamics, lung mechanics, gas exchange, lung fluid balance, lung histology, and the level of plasma cytokines were assessed.Results After 240 min of HF treatment there was a significant increase in cardiac output, reduction in pulmonary arterial pressure, and improvement in both oxygenation and lung mechanics. Also, in the HF group the lung wet-to-dry weight ratio was significantly reduced. Histologically, HF reduced edema and inflammatory cell infiltration in the lung. There was also a significantly greater decrease in plasma IL-6 and IL-8 levels in the HF group than in group receiving MV alone.Conclusions In a canine model of acute lung injury continuous HF improved cardiopulmonary function, reduced pulmonary edema, decreased lung permeability and inflammation, and decreased the plasma concentration of proinflammatory cytokines.     

长春新碱联合糖皮质激素治疗11例婴儿期Kasabach-Merritt综合征

目的 探讨Kasabach-Merritt（K-M）综合征的有效治疗方案。方法 收集2015—2017年首都医科大学附属北京儿童医院皮肤科收治的11例K-M综合征患儿的临床资料,分析长春新碱联合糖皮质激素治疗的疗效。结果 11例患儿就诊年龄1～212（87.91 ± 72.01） d,男4例、女7例。血管瘤多呈紫红色斑块,质地偏硬,其中5例瘤体周围伴有皮肤紫癜。血小板计数（4 ~ 32） × 109/L。给予口服泼尼松（2 ~ 5） mg·kg-1·d-1与静脉注射长春新碱每周0.05 mg/kg联合治疗。10例患儿应用糖皮质激素联合长春新碱治疗（1.8 ± 1.23）周后血小板达到正常,治疗（3.6 ± 1.26）周后纤维蛋白原恢复正常,治疗（3.9 ± 0.74）周后血管瘤开始软化或缩小。1例治疗5周后,血小板计数仍没有恢复正常,联合使用静脉栓塞后,血小板恢复正常,并可维持。结论 长春新碱联合糖皮质激素治疗可控制K-M综合征患儿瘤体发展,促进血小板恢复。