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.

Clinical Practice Status of Sentinel Lymph Node Biopsy for Early-Stage Breast Cancer Patients in China: A Multicenter Study

Background

Sentinel lymph node biopsy (SLNB) was introduced over 30 years ago, but the application of SLNB in China is unclear. This study aimed to explore the real-world implementation of SLNB among early-stage breast cancer patients in China.

Methods

A multi-center, retrospective study was conducted among primary breast cancer patients from 37 hospitals in China in 2018. Their clinical data were collected and analyzed, including the implementation status of SLNB in China, subsequent processing of sentinel lymph nodes (SLNs) containing metastases, and the effect of neoadjuvant chemotherapy (NAC) on SLNB.

Results

SLNB surgery was performed on 43.5% of early-stage breast cancer patients in China and 11,942 patients who underwent SLNB were enrolled in this study. The majority of SLNBs were performed using a single mapping agent. A combination of blue dye and radiotracer or fluorescence imaging was used in only 14.9% of patients. The mean (SD) number of resected SLNs was 4.0 (2.1). For the patients with 1 or 2 positive SLNs, 83.0% of them continued to receive axillary lymph node dissection (ALND), while others did not. For the patients with three or more positive SLNs, 97.2% of them continued to receive ALND, among which 82.9% accepted radiotherapy simultaneously. Of the patients who underwent SLN surgery, 5.5% (654/11,942) were receiving NAC. Among them, 51.9% received SLNB before NAC, and the rest received SLNB after NAC. In biopsy-proven positive nodes, 64.7% positive SLNs turned negative after NAC.

Conclusion

SLNB has been promoted in China, but it is not widely used compared to in developed countries. Furthermore, the usage of the dual tracer technique in SLNB is not high. Chinese breast surgeons are more conservative regarding the omission of ALND in 1 or 2 SLNs-positive patients.

[Autophagic dysfunction contributes to α-synuclein accumulation in dopaminergic neurons induced by paraquat]

Objective: To investigate the effects of Paraquat on autophagy level in SH-SY5Y cell and the mechanism of abnormal aggregation of α-synuclein. Methods: Human neuroblastoma cell (SH-SY5Y cell) was used as model of dopaminergic neurons in vitro. The cells were treated with different concentrations of PQ (0, 18.75, 37.5, 75, 150, 300, 600 μmol/L) for 24 hours, and induced by 150 μmol/L PQ for 0, 12, 24, 36, 48, 60, 72, 96 hours to detect the relative survival rate of cells and determine dose/time-effect relationship. The cells were treated with concentration of 0, 75, 150, 300, 600 μmol/L PQ for 24 hours, and induced by 150 μmol/L PQ for different hours to detect intracellular LDH activity. The expression levels of autophagy-related proteins(LC3I, LC3II, Beclin1 , Vps34 and p62) and α-synuclein were detected by Western blot. The gene expression level of α-synuclein was assayed by Real-time quantitative PCR. The expression level of α-synuclein was also evaluated by immunofluorescence. The cells were pretreated with 100 nmol/L autophagy inducer rapamycin (RAPA) for 6 hours. The expression levels of autophagy-related proteins and α-synuclein were detected by Western blot. Results: CCK8 assay showed PQ induced cell survival rate decrease in a time and dose dependent manner; Compared with control group, the activity of LDH in the cell supernatant increased significantly after PQ exposure (P<0.05) ; Western blot analysis showed the ratio of autophagy-related protein LC3II/LC3I, Beclin1 and Vps34 protein expression were significantly lower after PQ treatment while the expression of p62 protein was higher (P<0.05) ; The protein and gene expression of α-synuclein were increased significantly after PQ treatment (P <0.05) ; Immunofluorescence showed the fluorescence intensity of α- synuclein in cells was significantly enhanced (P <0.05) . Compared with PQ group, the expression levels of autophagy-related proteins LC3II/LC3I and Beclin1 were significantly increased whlie α-synuclein protein level was decreased after RAPA induction (P<0.05) . Similarly, the IF result showed the fluorescence signal of α- synuclein significantly decreased after RAPA induction (P<0.05) . Conclusion: Paraquat induced autophagy dysfunction in SH-SY5Y cells, which leads to an abnormal aggregation of α-synuclein.

[An epidemiological survey on clinical features, self-management and cognitive level of elderly asthmatics in China]

Objective: To investigate the prevalence of asthma among the elderly people in China and to analyze the clinical features, self-management and cognitive level of elderly asthma patients. Methods: According to the multi-stage random cluster sampling methods, a total of 164 215 subjects were visited by a questionnaire in the last epidemiology survey from eight provinces (Beijing, Shanghai, Guangdong, Liaoning, Henan, Shanxi, Jiangsu, Sichuan provinces) and seven regions (north, northeast, southern china, east, south, southwest and northwest) in China from February 2010 to August 2012. 2 034 were diagnosed as asthma. The elderly patients aged ≥65 years were selected from the 2 034 asthma patients. The clinical characteristics, comorbidities, the status of asthma control and self-management and insights of the disease in elderly asthma patients were analyzed. Results: Among the 2 034 asthma patients, 584 (28.7%) were elderly asthmatics aged ≥65 years old and 1 450 (71.3%) were<65 years old. In the elderly asthma group, Early-onset asthma accounted for 439 (75.2%) and 145 (24.8%) were late-onset. The common clinical manifestations of elderly asthma patients were: chest distress 395 (67.6%), wheezing 304 (52.1%), cough 298 (51.0%). Common comorbidities of elderly asthmatics were: chronic obstructive pulmonary disease 144 (24.7%), allergic rhinitis 122(20.9%), gastroesopheal reflux disease (GERD) 114(19.5%), allergic conjunctivitis 86 (14.7%), eczema 82 (14.0%), chronic bronchitis 76 (13.0%). The Asthma Control Test (ACT) scores of elderly asthmatics and non-elderly asthmatics were (18.5±3.2) and (21.7±3.4) respectively. There was a significant difference between the two groups (P=0.042). Of the elderly asthmatics, only 13 (2.2%) patients monitored daily using a peak flow meter. 93 (15.9%) patients aware that asthma was characterized by chronic airway inflammation. 64 (11.0%) asthmatics understood that the treatment goal. Conclusions: The clinical manifestations of elderly asthmatics are atypical, especially paroxysmal wheezing. Asthma in elderly people causes more comorbidities and mortality. The self-management and cognitive level of patients with asthma needs to be improved.

Proton transport enabled by a field-induced metallic state in a semiconductor heterostructure

Tuning a semiconductor to function as a fast proton conductor is an emerging strategy in the rapidly developing field of proton ceramic fuel cells (PCFCs). The key challenge for PCFC researchers is to formulate the proton-conducting electrolyte with conductivity above 0.1 siemens per centimeter at low temperatures (300 to 600°C). Here we present a methodology to design an enhanced proton conductor by means of a Na _x CoO₂/CeO₂ semiconductor heterostructure, in which a field-induced metallic state at the interface accelerates proton transport. We developed a PCFC with an ionic conductivity of 0.30 siemens per centimeter and a power output of 1 watt per square centimeter at 520°C. Through our semiconductor heterostructure approach, our results provide insight into the proton transport mechanism, which may also improve ionic transport in other energy applications.