Elastic wave velocity dispersion in polycrystals with elongated grains: Theoretical and numerical analysis

The phase velocity dispersion of longitudinal waves in polycrystals with elongated grains of arbitrary crystallographic symmetry is studied in all frequency ranges by the theoretical second-order approximation (SOA) and numerical three-dimensional finite element (FE) models. The SOA and FE models are found to be in excellent agreement for three studied polycrystals: cubic Al, Inconel, and a triclinic material system. A simple Born approximation for the velocity, not containing the Cauchy integrals, and the explicit analytical quasi-static velocity limit (Rayleigh asymptote) are derived. As confirmed by the FE simulations, the velocity limit provides an accurate velocity estimate in the low-frequency regime where the phase velocity is nearly constant on frequency; however, it exhibits dependence on the propagation angle. As frequency increases, the phase velocity increases towards the stochastic regime and then, with further frequency increase, behaves differently depending on the propagation direction. It remains nearly constant for the wave propagation in the direction of the smaller ellipsoidal grain radius and decreases in the grain elongation direction. In the Rayleigh and stochastic frequency regimes, the directional velocity change shows proportionalities to the two elastic scattering factors even for the polycrystal with the triclinic grain symmetry.

The association between napping and the risk of cardiovascular disease and all-cause mortality: a systematic review and dose-response meta-analysis

Background

Napping is a habit prevalent worldwide and occurs from an early age. Some sleep specialists have suggested it as a potential public health tool due to the prevalence of sleep disorder. However, the association between napping and the risk of cardiovascular disease (CVD) and all-cause mortality remains unclear.

Purpose

To assess the association between napping and the risk of CVD and all-cause mortality.

Methods

We conducted a systematic search of Medline, Embase and Cochrane databases from inception through December 2019 for prospective cohort studies investigating the association between napping and the risk of CVD and/or all-cause mortality. Overall estimates were calculated using random effect models with inverse variance weighting. Dose-response meta-analysis was performed using restricted cubic spline models. The results were reported as hazard ratio (HR) and 95% confidence interval (CI).

Results

A total of 313651 participants (57.8% female, 38.9% took naps) from 20 cohort studies were included in the analysis. Overall, pooled analysis detected no association between daytime nap and CVD (HR 1.13, 95% CI 0.99–1.28). However, in subgroup analysis including only participants who were female (HR 1.31, 95% CI 1.09–1.58), older (age>65 years) (HR 1.36, 95% CI 1.07–1.72), or took a longer nap (nap time>60 minutes) (HR 1.34, 95% CI 1.05–1.63), napping was significantly associated with a higher risk of CVD comparing to not napping. All-cause mortality was associated with napping overall (HR 1.19, 95% CI 1.12–1.26), and effect sizes were even more pronounced in females (HR 1.22, 95% CI 1.13–1.31), older participants (HR 1.27, 95% CI 1.11–1.45) and those who took a long nap (HR 1.30, 95% CI 1.12–1.47). Furthermore, after stratifying participants by night sleep time (<6 and >6h/day), no significant association was detected except those who slept >6h/day at night and took a long nap (HR 1.13, 95% CI 1.03–1.24). Dose-response analysis showed a J-curve relation between nap time and CVD (Figure 1). The HR decreased from 0 to 25 min/day, followed by a sharp increase in the risk at longer times. A positive linear relationship between nap time and all-cause mortality was also observed.

Conclusion

Long napping over 60 minutes per day is associated with increased risks of CVD and all-cause mortality. Night sleep duration may play a role in the relation between napping and all-cause mortality. Further, large-scale prospective cohort studies need to confirm our conclusion and investigate the underlying mechanisms driving these associations.

Funding Acknowledgement

Type of funding source: None

Gen-editing to model Short QT syndrome type 5 using human-induced pluripotent stem cell-derived cardiomyocytes

Aims

Short QT syndrome (SQTS), a disorder associated with characteristic electrocardiogram QT-segment abbreviation, predisposes afflicted patients to sudden cardiac death. Despite some progress in assessing the organ level pathophysiology and genetic changes of the disorder, the understanding of the human cellular phenotype and discovering of an optimal therapy has lagged due to a lack of appropriate human cellular models of the disorder. The aim of this study was to establish a cellular model of SQTS type 5 using human-induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) and gene-edited cell line using CRISPR/CAS9.

Methods and results

This study recruited one patient with short QT syndrome type 5 carrying a mutation in CACNb2 gene as well as one healthy control subject. We generated hiPSCs from their skin fibroblasts, and differentiated hiPSCs into cardiomyocytes (hiPSC-CMs) for physiological. Isogenic control hiPSC-CMs generated by the CRISPR/CAS9 technique were also used for the study.

The hiPSC-CMs from the patient showed a reduced calcium current (ICa-L) density and shortened action potential duration (APD) compared with healthy control hiPSC-CMs and isogenic hiPSC-CMs. Furthermore, they demonstrated abnormal rhythmic activities. Carbachol increased the arrhythmic events in SQTS significantly but not in healthy and isogenic control cells. Gene and protein expression profiling showed a decreased CACNb2 expression in SQTS cells. Quinidine prolonged the APD and abolished arrhythmic activity.

Conclusions

Patient-specific hiPSC-CMs are able to recapitulate single-cell phenotype features of SQTS type 5 and provide novel opportunities to further elucidate the cellular disease mechanism and test drug effects.

Funding Acknowledgement

Type of funding source: None

Abscisic acid and hydrogen peroxide are involved in drought priming-induced drought tolerance in wheat (Triticum aestivum L.)

Drought is one of the major stress factors in wheat production on a global scale. Drought priming during the early growth stage can enhance drought tolerance in wheat (Triticum aestivum L.). Abscisic acid (ABA) and hydrogen peroxide (H₂ O₂ ) are important signal molecules in the adaptation of plants to drought stress. However, the roles of ABA and H₂ O₂ in drought priming-induced drought tolerance are not clear. In the present study, we evaluated the responses of wheat to an ABA inhibitor, H₂ O₂ scavenger and an inhibitor to investigate the (i) relationship between ABA and H₂ O₂ in osmotic adjustment after drought priming in the vegetative stage and (ii) responses to drought stress during grain filling. In the drought priming alone treatments, chemical application resulted in the scavenging of ABA and H₂ O₂ , weakening the alleviation effects of drought priming on drought stress, as demonstrated by the lower leaf water potential and grain yield. The ABA inhibitor completely inhibited accumulation of ABA and H₂ O₂ ; the ABA inhibitor inhibited respiratory burst oxidase homologue expression, whereas the H₂ O₂ inhibitor resulted in higher 9-cis-epoxycarotenoid dioxygenase expression and ABA concentration in primed plants, indicating that ABA scavenging inhibited H₂ O₂ biosynthesis while H₂ O₂ scavenging did not inhibit ABA biosynthesis. The results further demonstrated that NADPH oxidase-mediated H₂ O₂ production functions downstream of ABA, which induces osmolyte transcript expression and accumulation, and thus contributes to drought priming-induced stress tolerance. These results provide a theoretical basis for a better understanding of the mechanisms involved in drought priming-induced tolerance in wheat plants.

Application of percutaneous transluminal sharp recanalization in transjugular intrahepatic portosystemic shunt for patients with chronic portal vein occlusion

PURPOSE

We aimed to evaluate the feasibility and safety of a modified technique for portal vein recanalization, percutaneous transluminal sharp recanalization (PTSR), when performing transjugular intrahepatic portosystemic shunt (TIPS) for the treatment of chronic portal vein occlusion (CPVO) and portal hypertension.

METHODS

Nine consecutive patients with CPVO and portal hypertension had undergone TIPS and PTSR procedure after failing in conventional percutaneous catheterization from March 2017 to July 2019. Technical success rates, effectiveness, and complications were evaluated. Follow-up of patients' clinical outcomes and shunt patency were performed periodically. Primary and secondary shunt patency were analyzed by Kaplan-Meier method.

RESULTS

The occluded portal veins were successfully recanalized after failing in conventional percutaneous catheterization, and TIPS procedures were completed in all 9 patients. Two patients suffered from procedure-related complications. A portosystemic pressure gradient <12 mmHg, or a percent reduction of 25% to 50% of baseline, was achieved in all 9 patients after TIPS. During the median follow-up period of 28 months (range, 9-36 months), 1 patient experienced recurrent ascites and the other 8 patients remained asymptomatic. The cumulative rates of primary and secondary shunt patency were 66.67% and 100%, respectively, at 2 years.

CONCLUSION

As a supplementary method, PTSR is a feasible and safe method for portal vein recanalization when performing TIPS for patients with CPVO and portal hypertension.

Maximizing the accuracy of finite element simulation of elastic wave propagation in polycrystals

Three-dimensional finite element (FE) modelling, with representation of materials at grain scale in realistic sample volumes, is capable of accurately describing elastic wave propagation and scattering within polycrystals. A broader and better future use of this FE method requires several important topics to be fully understood, and this work presents studies addressing this aim. The first topic concerns the determination of effective media parameters, namely, scattering induced attenuation and phase velocity, from measured coherent waves. This work evaluates two determination approaches, through-transmission and fitting, and it is found that these approaches are practically equivalent and can thus be used interchangeably. For the second topic of estimating modelling errors and uncertainties, this work performs thorough analytical and numerical studies to estimate those caused by both FE approximations and statistical considerations. It is demonstrated that the errors and uncertainties can be well suppressed by using a proper combination of modelling parameters. For the last topic of incorporating FE model information into theoretical models, this work presents elaborated investigations and shows that to improve agreement between the FE and theoretical models, the symmetry boundary conditions used in FE models need to be considered in the two-point correlation function, which is required by theoretical models.

Dental nerves: a neglected mediator of pulpitis

As one of the most densely innervated tissues, the dental pulp contains abundant nerve fibres, including sensory, sympathetic and parasympathetic nerve fibres. Studies in animal models and human patients with pulpitis have revealed distinct alterations in protein expression and histological appearance in all types of dental nerve fibres. Various molecules secreted by neurons, such as classical neurotransmitters, neuropeptides and amino acids, not only contribute to the induction, sensitization and maintenance of tooth pain, but also regulate non-neuronal cells, including fibroblasts, odontoblasts, immune cells and vascular endothelial cells. Dental nerves are particularly important for the microcirculatory and immune responses in pulpitis via their release of a variety of functional substances. Further, nerve fibres are found to be involved in dental soft and hard tissue repair. Thus, understanding how dental nerves participate in pulpitis could have important clinical ramifications for endodontic treatment. In this review, the roles of dental nerves in regulating pulpal inflammatory processes are highlighted and their implications for future research on this topic are discussed.