Blood-wall fluttering instability as a physiomarker of the progression of thoracic aortic aneurysms

The diagnosis of aneurysms is informed by empirically tracking their size and growth rate. Here, by analysing the growth of aortic aneurysms from first principles via linear stability analysis of flow through an elastic blood vessel, we show that abnormal aortic dilatation is associated with a transition from stable flow to unstable aortic fluttering. This transition to instability can be described by the critical threshold for a dimensionless number that depends on blood pressure, the size of the aorta, and the shear stress and stiffness of the aortic wall. By analysing data from four-dimensional flow magnetic resonance imaging for 117 patients who had undergone cardiothoracic imaging and for 100 healthy volunteers, we show that the dimensionless number is a physiomarker for the growth of thoracic ascending aortic aneurysms and that it can be used to accurately discriminate abnormal versus natural growth. Further characterization of the transition to blood-wall fluttering instability may aid the understanding of the mechanisms underlying aneurysm progression in patients.

The physical origin of aneurysm growth, dissection, and rupture

Rupture of aortic aneurysms is by far the most fatal heart disease, with a mortality rate exceeding 80%. There are no reliable clinical protocols to predict growth, dissection, and rupture because the fundamental physics driving aneurysm progression is unknown. Here, via in-vitro experiments, we show that a blood-wall, fluttering instability manifests in synthetic arteries under pulsatile forcing. We establish a phase space to prove that the transition from stable flow to unstable aortic flutter is accurately predicted by a flutter instability parameter derived from first principles. Time resolved strain maps of the evolving system reveal the dynamical characteristics of aortic flutter that drive aneurysm progression. We show that low level instability can trigger permanent aortic growth, even in the absence of material remodeling. Sufficiently large flutter beyond a secondary threshold localizes strain in the walls to the length scale clinically observed in aortic dissection. Lastly, significant physical flutter beyond a tertiary threshold can ultimately induce aneurysm rupture via failure modes reported from necropsy. Resolving the fundamental physics of aneurysm progression directly leads to clinical protocols that forecast growth as well as intercept dissection and rupture by pinpointing their physical origin.

The buckling-condensation mechanism driving gas vesicle collapse

Gas vesicles (GVs) are proteinaceous cylindrical shells found within bacteria or archea growing in aqueous environments and are composed primarily of two proteins, gas vesicle protein A and C (GvpA and GvpC). GVs exhibit strong performance as next-generation ultrasound contrast agents due to their gas-filled interior, tunable collapse pressure, stability in vivo and functionalizable exterior. However, the exact mechanism leading to GV collapse remains inconclusive, which leads to difficulty in predicting collapse pressures for different species of GVs and in extending favorable nonlinear response regimes. Here, we propose a two stage mechanism leading to GV loss of echogenicity and rupture under hydrostatic pressure: elastic buckling of the cylindrical shell coupled with condensation driven weakening of the GV membrane. Our goal is to therefore test whether the final fracture of the GV membrane occurs by the interplay of both mechanisms or purely through buckling failure as previously believed. To do so, we (1) compare the theoretical condensation and buckling pressures with that for experimental GV collapse and (2) describe how condensation can lead to plastic buckling failure. GV shell properties that are necessary input to this theoretical description, such as the elastic moduli and wettability of GvpA, are determined using molecular dynamics simulations of a novel structural model of GvpA that better represents the hydrophobic core. For GVs that are not reinforced by GvpC, this analytical framework shows that the experimentally observed pressures resulting in loss of echogenicity coincide with both the elastic buckling and condensation pressure regimes. We also found that the stress strain curve for GvpA wetted on both the interior and exterior exhibits a loss of mechanical stability compared to GvpA only wetted on the exterior by the bulk solution. We identify a pressure vs. vesicle size regime where condensation can occur prior to buckling, which may preclude nonlinear shell buckling responses in contrast imaging.

[Survey on present status of noise exposure of workers in metal processing industry]

Objective: To investigate the distribution of noise exposure between non-steady state noise and steady-state noise for metal processing workers, which will provide scientific basis for the prevention and treatment of noise hazards in metal processing industry. Methods: The cross-section method was used to investigate the noise exposure of 737 workers from three metal processing industries in Zhejiang Province from October to December 2017. The general demographic information and occupational history were collected by questionnaire. The noise was recorded by individual noise meters, and the noise exposure intensity (equivalent continuous A-weighted noise exposure level normalized to an 8 h-working-day, L(Aeq, 8 h)) and kurtosis were calculated. Results: Workers exposed to noise in the metal processing industry were mainly 18-40 years old (527 workers, 71.51%) , men (570 workers, 77.34%) , and junior high school education background (416 workers, 56.45%) . There were 572 workers (77.61%) with noise exposure intensity (L(Aeq, 8 h)) greater than 85 dB (A) , 558 workers (75.71%) exposed to non-steady state noise (kurtosis ≥4) , and 634 workers (86.02%) with exposure duration less than 8 years. Among the 30 work types investigated, the work types with noise intensity reaching 100% were the stamping, welding and others from a children's car manufacturing factory in Ningbo, operating, chamfering, tapping, and thread rolling from an automobile parts manufacturing factory in Ningbo; The work types with a rate of 100% exposed to non-steady state noise were the grinding from a children's car manufacturing factory in Ningbo, assembling, assembly operating and others from an automobile brake manufacturing factory in Wenzhou, and polishing from an automobile parts manufacturing factory in Ningbo. Conclusion: Metal processing workers have a high rate of over-standard exposed to high noise intensity and a high proportion exposed to non-steady state noise. It is necessary to take sound insulation and noise reduction engineering control, and strengthen personal protection and occupational health management measures to prevent and control the noise hazards.

Tetracycline as an inhibitor to the SARS-CoV-2

The coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains an extant threat against public health on a global scale. Cell infection begins when the spike protein of SARS-CoV-2 binds with the human cell receptor, angiotensin-converting enzyme 2 (ACE2). Here, we address the role of tetracycline as an inhibitor for the receptor-binding domain (RBD) of the spike protein. Targeted molecular investigation show that tetracycline binds more favorably to the RBD (-9.40 kcal/mol) compared to doxycycline (-8.08 kcal/mol), chloroquine (-6.31 kcal/mol), or gentamicin (-4.83 kcal/mol) while inhibiting attachment to ACE2 to a greater degree (binding efficiency of 2.98 kcal/(mol nm² ) for tetracycline-RBD, 5.16 kcal/(mol nm² ) for doxycycline-RBD, 5.59 kcal/(mol nm² ) for chloroquine-RBD, and 7.02 kcal/(mol nm² ) for gentamicin-RBD. Stronger inhibition by tetracycline is verified with nonequilibrium PMF calculations, for which the tetracycline-RBD complex exhibits the lowest free energy profile along the dissociation pathway from ACE2. Tetracycline binds to tyrosine and glycine residues on the viral contact interface that are known to modulate molecular recognition and bonding affinity. These RBD residues also engage in significant hydrogen bonding with the human receptor ACE2. The ability to preclude cell infection complements the anti-inflammatory and cytokine suppressing capability of tetracycline; this may reduce the duration of ICU stays and mechanical ventilation induced by the coronavirus SARS-CoV-2.

Thermodynamics of sustaining liquid water within rough icephobic surfaces to achieve ultra-low ice adhesion

The build-up of ice on aircraft, bridges, oil rigs, wind turbines, electrical lines, and other surfaces exposed to cold environments diminishes their safe and effective operation. To engineer robust surfaces that reduce ice adhesion, it is necessary to understand the physics of what makes a surface icephobic (“ice-hating”) as well as the relationship between icephobicity and ice adhesion. Here we elucidate the molecular origin of icephobicity based on ice-surface interactions and characterize the correlation between material icephobicity and liquid wettability. This fundamental understanding of icephobic characteristics enables us to propose a robust design for topologically textured, icephobic surfaces. The design identifies the critical confinement length scale to sustain liquid water (as opposed to ice) in between roughness features and can reduce the strength of ice adhesion by over a factor of twenty-seven compared to traditional hydrophobic surfaces. The reduction in ice adhesion is due to the metastability of liquid water; as ambient ice cleaves from the textured surface, liquid water leaves confinement and freezes – a process which takes the system from a local energy minimum to a global energy minimum. This phase transition generates a detachment force that actively propels ambient ice from the surface.

Spatial Distribution of Culex tritaeniorhynchus Giles, 1901 (Diptera: Culicidae) in Relation to Pigsties and Other Geo-environmental Features in Dao County, Hunan Province, China

In this study, we investigated the spatial distribution of Culex tritaeniorhynchus Giles, 1901 (Diptera: Culicidae) (the vector of Japanese B Encephalitis) and geo-environmental features (rice fields, forests, watercourses, and highways) correlated with their abundance in pigsties of Dao County, Hunan Province, China. First, light trapping in pigsties was carried out to determine vector density. Second, based on Advanced Land Observing Satellite remote-sensing datasets, spatial datasets of mosquito density and various geo-environmental features were constructed using Geography Information System. Finally, spatial statistical analysis and general linear regression were used to analyze the spatial distribution of vectors in relation to the geo-environmental features correlating with the abundance of mosquitoes in pigsties. As the results show, the distribution of mosquitoes in pigsties was not spatially autocorrelated, and several geo-environmental features that were either positively or negatively correlated with mosquito abundance in pigsties were identified. The application of these results to improve the control of vectors of Japanese B Encephalitis is also discussed.

Direct observation of the topological spin configurations mediated by the substitution of rare-earth element Y in MnNiGa alloy

The evolution of topological magnetic domains microscopically correlates the dynamic behavior of memory units in spintronic application. Nanometric bubbles with variation of spin configurations have been directly observed in a centrosymmetric hexagonal magnet (Mn_0.5Ni_0.5)₆₅(Ga_1-yY_y)₃₅ (y = 0.01) using Lorentz transmission electron microscopy. Magnetic bubbles instead of biskyrmions are generated due to the enhancement of quality factor Q caused by the substitution of rare-earth element Y. Furthermore, the bubble density and diversified spin configurations are systematically manipulated via combining the electric current with perpendicular magnetic fields. The magnetic bubble lattice at zero field is achieved after the optimized manipulation.

Efficacy of Omega-3 Polyunsaturated Fatty Acids Supplementation in Managing Overweight and Obesity: A Meta-Analysis of Randomized Clinical Trials

OBJECTIVE

Studies in rodents and humans have indicated that omega-3 polyunsaturated fatty acids (n-3 PUFA) may reduce weight. The aim of this meta-analysis was to evaluate evidence for the efficacy of n-3 PUFA in managing overweight and obesity.

METHODS

We performed a systematic search of PubMed, Embase, and Cochrane Central Register of Controlled Trials until May 2015. Two reviewers independently determined the eligibility of studies and assessed the reporting quality of included randomized controlled trials (RCTs).

RESULTS

A total of 11 RCTs involving 617 participants were included in this meta-analysis. Based on the meta-analysis of nine studies, a statistically nonsignificant difference was revealed in weight loss between n-3 PUFA and placebo (p=0.99; weighted mean difference [WMD]: 0.00; 95% confidence interval [CI] -0.42 to 0.43), whereas n-3 PUFA was superior to placebo in reducing serum triglyceride levels (p=0.0007; standard median difference [Std MD]: -0.59; 95% CI -0.93 to -0.25). Based on meta-analysis of seven studies, the analysis of aggregated data showed a significant reduction in waist circumference (p=0.005; WMD: -0.53; 95% CI -0.90 to -0.16). There were no significant differences in body mass index, total serum levels of cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and fasting glucose levels.

CONCLUSIONS

The evidence from RCTs showed that n-3 PUFA might effectively reduce waist circumference and triglyceride levels in overweight and obese adults, but n-3 PUFA may not effectively reduce body weight. Given the small number and poor quality of RCTs included in the meta-analysis, these results are inconclusive. A large-scale, well-designed RCT is needed to further address this issue.

A preliminary investigation of the mechanisms underlying the effect of berberine in preventing high-fat diet-induced insulin resistance in rats

Berberine exerts insulin resistance-improving effects, the underlying mechanism of which is not well understood. We herein aimed to examine the effects of berberine on mediators of insulin signaling in pancreatic β- and α- islet cells and hepatocytes using a rat obesity model. Rats were fed the following diets for 22 weeks: normal control (NC); normal+berberine (NC+BBR 200 mg/kg/day); high-fat (HF); HF+BBR(1) (BBR 100 mg/kg/day); HF+BBR(2) (BBR 200 mg/kg/day). Metabolic parameters were assessed and mediators of insulin signaling were quantified by immunohistochemistry. The HF diet significantly increased body weight (BW), visceral fat (VF), the visceral fat to BW ratio (VF/BW), and insulin resistance index in the HF group compared with the NC group. Both doses of BBR significantly reduced HF diet-induced increases in BW, VF, and VF/BW. IR and IRS-1 expression in β-cells was significantly lower in the HF group, but not the HF+BBR groups, compared with the NC and NC+BBR groups. Glucagon expression in α-cells was significantly higher in the HF group compared with all other groups. IR expression in α-cells was significantly lower in the HF group compared with the NC, NC+BBR, and HF+BBR(2) groups. IR expression in hepatocytes was significantly lower in the HF group compared with all groups. Our preliminary findings suggest that berberine may ameliorate the development of insulin resistance by differentially preventing alterations in expression of IR, IRS-1, and glucagon in β-cells, α-cells, and hepatocytes.