Value of multiple models of diffusion-weighted imaging to predict hepatic lymph node metastases in colorectal liver metastases patients

BACKGROUND About 10%-31% of colorectal liver metastases(CRLM)patients would concomitantly show hepatic lymph node metastases(LNM),which was considered as sign of poor biological behavior and a relative contraindication for liver resection.Up to now,there’s still lack of reliable preoperative methods to assess the status of hepatic lymph nodes in patients with CRLM,except for pathology examination of lymph node after resection.AIM To compare the ability of mono-exponential,bi-exponential,and stretchedexponential diffusion-weighted imaging(DWI)models in distinguishing between benign and malignant hepatic lymph nodes in patients with CRLM who received neoadjuvant chemotherapy prior to surgery.METHODS In this retrospective study,97 CRLM patients with pathologically confirmed hepatic lymph node status underwent magnetic resonance imaging,including DWI with ten b values before and after chemotherapy.Various parameters,such as the apparent diffusion coefficient from the mono-exponential model,and the true diffusion coefficient,the pseudo-diffusion coefficient,and the perfusion fraction derived from the intravoxel incoherent motion model,along with distributed diffusion coefficient(DDC)andαfrom the stretched-exponential model(SEM),were measured.The parameters before and after chemotherapy were compared between positive and negative hepatic lymph node groups.A nomogram was constructed to predict the hepatic lymph node status.The reliability and agreement of the measurements were assessed using the coefficient of variation and intraclass correlation coefficient.RESULTS Multivariate analysis revealed that the pre-treatment DDC value and the short diameter of the largest lymph node after treatment were independent predictors of metastatic hepatic lymph nodes.A nomogram combining these two factors demonstrated excellent performance in distinguishing between benign and malignant lymph nodes in CRLM patients,with an area under the curve of 0.873.Furthermore,parameters from SEM showed substantial repeatability.CONCLUSION The developed nomogram,incorporating the pre-treatment DDC and the short axis of the largest lymph node,can be used to predict the presence of hepatic LNM in CRLM patients undergoing chemotherapy before surgery.This nomogram was proven to be more valuable,exhibiting superior diagnostic performance compared to quantitative parameters derived from multiple b values of DWI.The nomogram can serve as a preoperative assessment tool for determining the status of hepatic lymph nodes and aiding in the decision-making process for surgical treatment in CRLM patients.

Hepatic artery infusion with raltitrexed or 5-fluorouracil for colorectal cancer liver metastasis

AIM To evaluate the efficiency and safety of hepatic artery infusion chemotherapy(HAIC) using raltitrexed or 5-fluorouracil for colorectal cancer(CRC) liver metastasis(CRCLM).METHODS A retrospective analysis of patients with unresectable CRCLM who failed systemic chemotherapy and were subsequently treated with HAIC at our institute from May 2013 to April 2015 was performed. A total of 24 patients were treated with 5-fluorouracil, and 18 patients were treated with raltitrexed. RESULTS The median survival time(MST) from diagnosis of CRC was 40.8 mo in the oxaliplatin plus raltitrexed(TOMOX) arm and 33.5 mo in the oxaliplatin plus 5-fluorouracil(FOLFOX) arm(P = 0.802). MST from first HAIC was 20.6 mo in the TOMOX arm and 15.4 mo in the FOLFOX arm(P = 0.734). Median progression-free survival(PFS) from first HAIC was 4.9 mo and 6.6 mo, respectively, in the TOMOX arm and FOLFOX arm(P= 0.215). Leukopenia(P = 0.026) was more common in the FOLFOX arm, and hepatic disorder(P = 0.039) was more common in the TOMOX arm. There were no treatment-related deaths in the TOMOX arm and one treatment-related death in the FOLFOX arm. Analysis of prognostic factors indicated that response to HAIC was a significant factor related to survival.CONCLUSION No significant difference in survival was observed between the TOMOX and FOLFOX arms. HAIC treatment with either TOMOX or FOLFOX was demonstrated as an efficient and safe alternative choice.

Impact of Serum Vascular Endothelial Growth Factor on Prognosis in Patients with Unresectable Hepatocellular Carcinoma after Transarterial Chemoembolization

Objective： To investigate the expression level with unresectable hepatocellular carcinoma （HCC） and to assess the impact of serum VEGF as chemoembolization （TACE） treatments. of serum vascular endothelial growth factor （VEGF） in patients and its relationship with the c a predictive factor for HCC nicopathological characteristics, prognosis during transarterial Methods： Serum VEGF levels were measured using enzyme-linked immunosorbent assay （ELISA） in 60 random patients who underwent TACE or transarterial infusion （TAI） for unresectable HCC between May and September 2008 and 12 healthy volunteers were also involved in this study to serve as control. All patients＇ clinicopathological features were retrospectively analyzed. Serum VEGF levels were correlated with clinicopathological features of the HCC patients. The patients＇ survival rates were analyzed with Kaplan-Meier survival curves and compared by the log-rank test. The prognostic significance of serum VEGF levels and factors related to survival rate were evaluated by univariate and multivariate analysis. Results： The median serum VEGF level in the HCC patients was 285 pg/ml （range 14-1,207 pg/ml）, significantly higher than that of healthy controls （P=0.021）. The serum VEGF levels were significantly correlated with platelet counts （r=0.396, P=0.002） but not other clinicopathological features. Patients with serum VEGF level 〉285 pg/ml had worse overall survival compared with those with serum VEGF level 〈285 pg/ml （P=0.002）. By multivariate analysis, the serum VEGF level was a significant prognostic factor. Conclusion： High serum VEGF levels may predict poor prognosis of HCC after TACE. This study highlights the importance of tumor biomarker as a prognostic predictor in TACE therapy for HCC, which has an intrinsic problem of unavailability of histopathological prognostic features.

Feasibility of differentiating T3 from T4a gastric cancer in different Lauren classification by determining serosa invasion：Diagnostic performance of high enhanced serosa sign

Objective： To study the value of high enhanced serosa sign on contrast-enhanced computed tomography（CT）in differentiating T3 from T4a gastric cancer in different Lauren classification.Methods： This study included 276 consecutive patients with surgically confirmed p T3 or p T4a gastric cancers.The pre-operative CT images were reviewed by two radiologists blinded. The demonstration of the high enhanced serosa on CT between T3 and T4a was compared with chi-square test. The diagnostic performance of this sign on CT in the differentiation of T4a from T3 in different Lauren classification was calculated.Results： The accuracy, sensitivity, specificity, positive predictive value（PPV） and negative predictive value（NPV） for the judgement of serosa invasion using the high enhanced serosa sign on CT was 74.6%, 63.7%, 83.6%,76.0% and 73.8% by one radiologist and 76.4%, 66.1%, 84.9%, 78.1% and 75.4% by the other radiologist.Compared to the intestinal-type, the sensitivity of the judgement of serosa invasion using the high enhanced serosa sign on CT in diffuse-type was significant higher（80% in both readers）, while the specificity trended to be lower（65.9% and 80.5%, respectively）. There is no significant difference in the accuracy of diagnosis between intestinaltype and diffuse-type of gastric cancers（the P-values of two radiologists were 0.968, 0.591, respectively）. The combination of the high enhanced serosa sign with conventional CT signs is significant different in diagnosis of T3 and T4a（P〈0.001）. The diagnostic accuracy was increased in both radiologists after the combination. The two readers achieved substantial agreement, with Kappa coefficient of 0.63, P〈0.001.Conclusions： The high enhanced serosa sign on CT is associated with serosa involvement. The sensitivity of the judgement of serosa invasion using this sign on CT in diffuse-type was significant higher than that in intestinal-type.

Transarterial chemoembolization with hepatic arterial infusion chemotherapy plus S-1 for hepatocellular carcinoma

BACKGROUND Transarterial chemoembolization(TACE)and hepatic arterial infusion chemotherapy(HAIC)have shown promising local benefits for advanced hepatocellular carcinoma(HCC).S-1,a composite preparation of a 5-fluorouracil prodrug,has proven to be a convenient oral chemotherapeutic agent with definite efficacy against advanced HCC.AIM To evaluate the efficacy and safety of TACE followed by HAIC with or without oral S-1 for treating advanced HCC.METHODS In this single-center,open-label,prospective,randomized controlled trial,117 participants with advanced HCC were randomized to receive TACE followed by oxaliplatin-based HAIC either with(TACE/HAIC+S-1,n=56)or without(TACE/HAIC,n=61)oral S-1 between December 2013 and September 2017.Two participants were excluded from final analysis for withdrawing consent.The primary endpoint was progression-free survival(PFS)and secondary endpoints included overall survival(OS),objective response rate,disease control rate and safety.RESULTS In total,115 participants(100 males and 15 females;mean age,57.7 years±11.9)were analyzed.The median PFS and OS were 5.0 mo(0.4–58.6 mo)(95%confidence interval(CI):3.82 to 6.18)vs 4.4 mo(1.1–54.4 mo)(95%CI:2.54 to 6.26;P=0.585)and 8.4 mo(0.4–58.6 mo)(95%CI:6.88 to 9.92)vs 8.3 mo(1.4–54.4 m)(95%CI:5.71 to 10.96;P=0.985)in the TACE/HAIC+S-1 and TACE/HAIC groups,respectively.The objective response rate and disease control rate were 30.9%vs 18.4%and 72.7%vs 56.7%in the TACE/HAIC+S-1 and TACE/HAIC groups,respectively.Grade 3/4 adverse events had a similar frequency in both treatment groups.CONCLUSION No improvements in tumor response rates,PFS or OS were observed with the addition of S-1 to TACE/HAIC in advanced HCC.Both treatment regimens had a similar safety profile.

Responses from two firing patterns in inferior colliculus neurons to stimulation of the lateral lemniscus dorsal nucleus

The γ-aminobutyric acid neurons（GABAergic neurons） in the inferior colliculus are classified into various patterns based on their intrinsic electrical properties to a constant current injection. Although this classification is associated with physiological function, the exact role for neurons with various firing patterns in acoustic processing remains poorly understood. In the present study, we analyzed characteristics of inferior colliculus neurons in vitro, and recorded responses to stimulation of the dorsal nucleus of the lateral lemniscus using the wholecell patch clamp technique. Seven inferior colliculus neurons were tested and were classified into two firing patterns： sustained-regular（n = 4） and sustained-adapting firing patterns（n = 3）. The majority of inferior colliculus neurons exhibited slight changes in response to stimulation and bicuculline. The responses of one neuron with a sustained-adapting firing pattern were suppressed after stimulation, but recovered to normal levels following application of the γ-aminobutyric acid receptor antagonist. One neuron with a sustained-regular pattern showed suppressed stimulation responses, which were not affected by bicuculline. Results suggest that GABAergic neurons in the inferior colliculus exhibit sustained-regular or sustained-adapting firing patterns. Additionally, GABAergic projections from the dorsal nucleus of the lateral lemniscus to the inferior colliculus are associated with sound localization. The different neuronal responses of various firing patterns suggest a role in sound localization. A better understanding of these mechanisms and functions will provide better clinical treatment paradigms for hearing deficiencies.

Preoperative prediction of malignant potential of 2-5 cm gastric gastrointestinal stromal tumors by computerized tomography-based radiomics

BACKGROUND The use of endoscopic surgery for treating gastrointestinal stromal tumors(GISTs)between 2 and 5 cm remains controversial considering the potential risk of metastasis and recurrence.Also,surgeons are facing great difficulties and challenges in assessing the malignant potential of 2-5 cm gastric GISTs.AIM To develop and evaluate computerized tomography(CT)-based radiomics for predicting the malignant potential of primary 2-5 cm gastric GISTs.METHODS A total of 103 patients with pathologically confirmed gastric GISTs between 2 and 5 cm were enrolled.The malignant potential was categorized into low grade and high grade according to postoperative pathology results.Preoperative CT images were reviewed by two radiologists.A radiological model was constructed by CT findings and clinical characteristics using logistic regression.Radiomic features were extracted from preoperative contrast-enhanced CT images in the arterial phase.The XGboost method was used to construct a radiomics model for the prediction of malignant potential.Nomogram was established by combing the radiomics score with CT findings.All of the models were developed in a training group(n=69)and evaluated in a test group(n=34).RESULTS The area under the curve(AUC)value of the radiological,radiomics,and nomogram models was 0.753(95%confidence interval[CI]:0.597-0.909),0.919(95%CI:0.828-1.000),and 0.916(95%CI:0.801-1.000)in the training group vs 0.642(95%CI:0.379-0.870),0.881(95%CI:0.772-0.990),and 0.894(95%CI:0.773-1.000)in the test group,respectively.The AUC of the nomogram model was significantly larger than that of the radiological model in both the training group(Z=2.795,P=0.0052)and test group(Z=2.785,P=0.0054).The decision curve of analysis showed that the nomogram model produced increased benefit across the entire risk threshold range.CONCLUSION Radiomics may be an effective tool to predict the malignant potential of 2-5 cm gastric GISTs and assist preoperative clinical decision making.

A 5.12-GHz LC-based phase-locked loop for silicon pixel readouts of high-energy physics

There is an urgent need for high-quality and high-frequency clock generators for high-energy physics experiments.The transmission data rate exceeds 10 Gbps for a single channel in future readout electronics of silicon pixel detectors.Others,such as time measurement detectors,require a high time resolution based on the time-to-digital readout architecture.A phase-locked loop(PLL)is an essential and broadly used circuit in these applications.This study presents an application-specific integrated circuit of a low-jitter,low-power LC-tank that is PLL fabricated using 55-nm CMOS technology.It includes a 3rd-order frequency synthesis loop with a programmable bandwidth,a divide-by-2 pre-scaler,standard low-voltage differential signaling interfaces,and a current mode logic(CML)driver for clock transmissions.All the d-flip-flop dividers and phase-frequency detectors are protected from single-event upsets using the triple modular redundancy technique.The proposed VCO uses low-pass filters to suppress the noise from bias circuits.The tested LC-PLL covers a frequency locking range between 4.74 GHz and 5.92 GHz with two sub-bands.The jitter measurements of the frequency-halved clock(2.56 GHz)are less than 460 fs and 0.8 ps for the random and deterministic jitters,respectively,and a total of 7.5 ps peak-to-peak with a bit error rate of 10^(-12).The random and total jitter values for frequencies of 426 MHz and 20 MHz are less than 1.8 ps and 65 ps,respectively.The LC-PLL consumed 27 mW for the core and 73.8 mW in total.The measured results nearly coincided with the simulations and validated the analyses and tests.

Primary extra-pancreatic pancreatic-type acinar cell carcinoma in the right perinephric space: A case report and review of literature

BACKGROUND Primary extra-pancreatic pancreatic-type acinar cell carcinoma(ACC)is a rare malignancy,and has only been reported in the gastrointestinal tract,liver,and lymph nodes until now.Extra-pancreatic pancreatic-type ACC in the perinephric space has not been reported.Herein,we report the first case of ACC in the perinephric space and describe its clinical and imaging features,which should be considered when differentiating perinephric space neoplasms.CASE SUMMARY A 48-year-old man with a 5-year history of hypertension was incidentally found to have an asymptomatic right retroperitoneal mass during a routine health check-up.Laboratory tests were normal.Abdominal computed tomography and magnetic resonance imaging showed an oval hypervascular mass with a central scar and enhanced capsule in the right perinephric space.After surgical resection of the neoplasm,the diagnosis was primary extra-pancreatic pancreatic-type ACC.The patient was alive without recurrence or metastasis during a 15-mo follow-up.CONCLUSION This is the first report of an extra-pancreatic ACC in right perinephric space,which should be considered as a possible diagnosis in perinephric tumors.

Early warning prevention and control strategies to reduce perioperative venous thromboembolism in patients with gastrointestinal cancer

BACKGROUND Venous thromboembolism(VTE)is a major cause of unexpected and perioperative in-hospital deaths.It is characterized by high morbidity,high mortality,high misdiagnosis rate,and high missed diagnosis rates.VTE is a common postoperative complication in cancer patients.VTE is preventable,and early identification of risk factors leading to VTE and appropriate early preventive actions can reduce its occurrence and mortality.Presently,there is no uniform standard for the prevention and control of VTE in clinical practice,and hospitals in China lack mature and effective protocols for the assessment,prevention,and treatment of VTE.AIM To explore whether an early warning program could influence the occurrence of deep vein thrombosis(DVT)postoperatively.METHODS This is a comparative retrospective cohort study,which enrolled patients who underwent laparotomic or laparoscopic gastrointestinal tumor resection for gastrointestinal cancer between January 2016 and December 2019.Patients were divided into a control group and an early warning group depending on whether or not the early warning program was implemented.A venous thromboembolism prevention and control team was established.The outcomes included the occurrence of DVT,the correct rate of VTE assessment,the coagulation indicators,and the mastery of VTE knowledge by the nurses.RESULTS A total of 264 patients were included in this study,with 128 patients in the control group and 136 patients in the early warning group.The occurrence rate of DVT in the early warning group was 6.6%(9/136),compared with 14.1%(18/128)in the control group(P<0.05).The correct rates of VTE risk assessment by the nurses and standard implementation rate of VTE preventive measures were 86.8%vs 65.6%and 80.2%vs 57.8%in early warning and control groups,respectively(all P<0.001).The independent factors associated with postoperative DVT occurrence were age(OR=1.083,95%CI:1.070-3.265,P=0.032),Hyperlipidemia(OR=1.127,95%CI:1.139-2.564,P=0.042),preoperative high VTE risk(OR=2.131,95%CI:1.085-5.178,P=0.001),time of operation(OR=2.268,95%CI:2.005-5.546,P=0.026)and not adoption of early warning prevention(OR=3.747,95%CI:1.523-6.956,P=0.017).CONCLUSION The early warning strategy was independently associated with the decreasing occurrence of VTE,and it might be suitable for protection from VTE in patients undergoing gastrointestinal cancer surgery.

Prediction of the lymphatic,microvascular,and perineural invasion of pancreatic neuroendocrine tumors using preoperative magnetic resonance imaging

BACKGROUND Significant correlation between lymphatic,microvascular,and perineural invasion(LMPI)and the prognosis of pancreatic neuroendocrine tumors(PENTs)was confirmed by previous studies.There was no previous study reported the relationship between magnetic resonance imaging(MRI)parameters and LMPI.AIM To determine the feasibility of using preoperative MRI of the pancreas to predict LMPI in patients with non-functioning PENTs(NFPNETs).METHODS A total of 61 patients with NFPNETs who underwent MRI scans and lymphadenectomy from May 2011 to June 2018 were included in this retrospective study.The patients were divided into group 1(n=34,LMPI negative)and group 2(n=27,LMPI positive).The clinical characteristics and qualitative MRI features were collected.In order to predict LMPI status in NF-PNETs,a multivariate logistic regression model was constructed.Diagnostic performance was evaluated by calculating the receiver operator characteristic(ROC)curve with area under ROC,sensitivity,specificity,positive predictive value(PPV),negative predictive value(NPV)and accuracy.RESULTS There were significant differences in the lymph node metastasis stage,tumor grade,neuron-specific enolase levels,tumor margin,main pancreatic ductal dilatation,common bile duct dilatation,enhancement pattern,vascular and adjacent tissue involvement,synchronous liver metastases,the long axis of the largest lymph node,the short axis of the largest lymph node,number of the lymph nodes with short axis>5 or 10 mm,and tumor volume between two groups(P<0.05).Multivariate analysis showed that tumor margin(odds ratio=11.523,P<0.001)was a predictive factor for LMPI of NF-PNETs.The area under the receiver value for the predictive performance of combined predictive factors was 0.855.The sensitivity,specificity,PPV,NPV and accuracy of the model were 48.1%(14/27),97.1%(33/34),97.1%(13/14),70.2%(33/47)and 0.754,respectively.CONCLUSION Using preoperative MRI,ill-defined tumor margins can effectively predict LMPI in patients with NF-PNETs.

人工智能在宁夏银川社区糖尿病视网膜病变远程筛查中的应用

目的:评估人工智能(AI)辅助诊断系统在宁夏银川社区糖尿病视网膜病变(DR)筛查中的应用效果。方法:收集2020-07/2021-07就诊于宁夏银川两个社区卫生服务中心的2型糖尿病患者1358例2707眼的眼底彩照,采用Eye Wisdom AI眼病辅助筛查和诊断系统自动检测分析出血、微动脉瘤以及视网膜内微血管异常等DR的特征性改变。根据其国际分期的标准对眼底彩照检测结果进行自动分级,由人工分析组进行图像判读后反馈结果,分析AI辅助筛查系统诊断DR的灵敏度、特异度、误诊率及漏诊率,比较AI与人工分析的一致性,对AI筛查系统与人工分析的结果做Kappa一致性检验。结果:与人工分析相比,AI诊断有无DR的灵敏度为91.84%,特异度为99.06%,漏诊率为8.16%,误诊率为0.94%,对于二者诊断结果的一致性分析Kappa值为0.817(P<0.001)。与人工分析相比,AI组检测无DR的灵敏度为99.06%,特异度为91.84%;检测轻度NPDR的灵敏度为85.36%,特异度为98.52%;中度NPDR的灵敏度为81.53%,特异度为98.55%;重度NPDR的灵敏度为70%,特异度为99.51%;PDR的灵敏度为86.67%,特异度为99.63%。二者对DR分期诊断一致性分析的Kappa值为0.878(P<0.01)。结论:AI辅助筛查系统与人工分析的结果一致性好,可以满足DR筛查的需求,为基层社区DR患者提供了一种新的有效防治模式。

Spectral CT imaging as a new quantitative tool? Assessment of perfusion defects of pulmonary parenchyma in patients with lung cancer

Objective： This study investigated the capability of dual-energy spectral computed tomography （CT） to quantitatively evaluate lung perfusion defects that are induced by central lung cancer. Methods： Thirty-two patients with central lung cancer underwent CT angiography using spectral imaging. A univariate general linear model was conducted to analyze the variance of iodine concentration/CT value with three factors of lung fields. A paired t-test was used to compare iodine concentrations and CT values between the distal end of lung cancer and the corresponding area in the contralateral normal lung. Results： Iodine concentrations increased progressively in the far, intermediate and near ground sides in the normal lung fields at 0.60±0.28, 0.93±0.27 and 1.25±0.38 mg/mL, respectively （P〈0.001）. The same trend was observed for the CT values [-（840.64±49.08）, -（812.66±50.85） and -（760.83±89.17） HU, P〈0.001]. The iodine concentration （0.70±0.42 mg/mL） of the lung field in the distal end of lung cancer was significantly lower than the corresponding area in the contralateral normal lung （1.19±0.62 mg/mL） （t=-7.23, P〈0.001）. However, the CT value of lung field in the distal end of lung cancer was significantly higher than the corresponding area in the contralateral normal lung [-（765.29±93.34） HU vs. -（800.07±76.18） HU, t=3.564, P=0.001]. Conclusions： Spectral CT imaging based on the spectral differentiation of iodine is feasible and can quantitatively evaluate pulmonary perfusion and identify perfusion defects that are induced by central lung cancer. Spectral CT seems to be a promising technique for the simultaneous evaluation of both morphological and functional lung information.

Fused monochromatic imaging acquired by single source dual energy CT in hepatocellular carcinoma during arterial phase: an initial experience

Objective： To explore whether single and fused monochromatic images can improve liver tumor detection and delineation by single source dual energy CT （ssDECT） in patients with hepatocellular carcinoma （HCC） during arterial phase. Methods： Fifty-seven patients with HCC who underwent ssDECT scanning at Beijing Cancer Hospital were enrolled retrospectively. Twenty-one sets of monochromatic images from 40 to 140 keV were reconstructed at 5 keV intervals in arterial phase. The optimal contrast-noise ratio （CNR） monochromatic images of the liver tumor and the lowest-noise monochromatic images were selected for image fusion. We evaluated the image quality of the optimal-CNR monochromatic images, the lowest-noise monochromatic images and the fused monochromatic images, respectively. The evaluation indicators included the spatial resolution of the anatomical structure, the noise level, the contrast and CNR of the tumor. Results： In arterial phase, the anatomical structure of the liver can be displayed most clearly in the 65-keV monochromatic images, with the lowest image noise. The optimal-CNR monochromatic images of HCC tumor were 50-keV monochromatic images in which the internal structural features of the liver tumors were displayed most clearly and meticulously. For tumor detection, the fused monochromatic images and the 50-keV monochromatic images had similar performances, and were more sensitive than 65-keV monochromatic images. Conclusions： We achieved good arterial phase images by fusing the optimal-CNR monochromatic images of the HCC tumor and the lowest-noise monochromatic images. The fused images displayed liver tumors and anatomical structures more clearly, which is potentially helpful for identifying more and smaller HCC tumors.

Factors Influencing Subjective Orthodontic Treatment Need and Culture-related Differences among Chinese Natives and Foreign Inhabitants

Aim The aim of this survey was to compare Chinese natives and foreign inhabitants in Chengdu, China, with respect to： （1） attitudes towards dental appearance, （2） subjective orthodontic treatment need, and （3） the main factors influencing orthodontic treatment need. Methodology A total of 522 subjects, including 227 foreign inhabitants and 295 Chinese natives in Chengdu participated in the survey. A simple random sampling method was adopted and a face-to-face interview was conducted at some public sites using a questionnaire. Data was entered by two persons synchronously using Epidata 3.0, and SPSS 13.0 was used to analyze these data. Results 89.0% of foreign inhabitants were satisfied with their teeth compared to only 46.8% of Chinese natives. Females were more dissatisfied with their teeth than males. Chinese natives put improving appearance as the top priority （55.9%） for seeking orthodontic treatment; however, in foreign inhabitants, the main reason for seeking treatment was to improve masticatory function（44.1%）, followed by ＂to be pretty＂ （35.2%）. The importance of well-aligned teeth and self-perception of psychosocial impact of malocclusion were the same two main factors influencing subjective orthodontic treatment need （P〈0.05） in foreign inhabitants and Chinese natives. Sub- jective orthodontic treatment need between the two target groups was significantly different （P〈0.05）. Conclusion （1） It was very common that Chinese natives were dissatisfied with their dental appearance, and their subjective orthodontic treatment needs were high. （2） There were some differences in orthodontic treatment motives between the two target groups. （3） There were differences in subjective orthodontic treatment needs between foreign inhabitants and Chinese natives. However, the prominent influential factors were almost the same. There may be benefit to understanding subjective orthodontic needs of different races.

First-Principles Study of Ultrathin Molybdenum Sulfides Nanowires:Electronic and Catalytic Hydrogen Evolution Properties

Molybdenum sulfides nanomaterials, such as one-dimensional (1D) nanotubes, nanoribbons, and two-dimensional (2D) nanosheets, have attracted intensive research interests for their novel electronic, optical, and catalytic properties. On the basis of first-principles calculation, here, we report a new series of 1D ultrathin molybdenum sulfides nanowires, including Mo2S6、Mo3S6 and Mo6S10 nanowires. Our results demonstrate that these ultrathin nanowires are both thermal and lattices dynamically stable, confirmed with the calculated phonon spectrum and Born-Oppenheimer molecular dynamic simulation at the temperature up to 600 K. The calculated elastic constant is 21.33, 103.22, and 163.00 eV/■ for Mo2S6, Mo3S6, and Mo6S10 nanowires, respectively. Mo2S6 and Mo3S6 nanowires are semiconductors with band gap of 1.55 and 0.46 eV, while Mo6S10 nanowires is metal, implying their potential applications in electronics and optoelectronics. In particular, ultrathin molybdenum sulfides nanowires can be used as catalysts for hydrogen evolution reaction. The calculated Gibbs free energy change for hydrogen evolution is about -0.05 eV for Mo2S6 nanowire, comparable with those of Pt and H-MoS2. The prediction of these 1D molybdenum sulfides nanowires may enrich the 1D family molybdenum sulfides and make a supplement to understand the high performance of hydrogen evolution reaction in transition-metal dichalcogenides.

In vitro Degradation of Pure Mg for Esophageal Stent in Artificial Saliva

Magnesium and its alloys as biodegradable implant materials can be potentially used in cardiovascular and orthopedic devices. However, few studies have focused on its application in esophageal stents. In this paper, time-lapse degradation characteristics of pure Mg were analyzed by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, hydrogen evolution, pH and electrochemical measurements after immersion in artificial saliva for different times. Results revealed that a dense degradation product film formed on samples, which mainly consisted of two kinds of layers： one was calcium phosphate compounds with different structures; the other was thin magnesium hydrate layer close to the substrate. Less pH increase and low degradation rate were ob- served in the first 5 days of immersion, which can be ascribed to the formation of a thicker and denser layer on the sample surface with increasing immersion time. And then there was an increase in degradation rate and pH values; the deposition layer remained almost intact after immersion for 6 and 8 days. After 10 days of immersion, the degradation rate and pH value remained stable, and the calcium phosphate layer was delaminated and the inner magnesium hydrate layer was exposed. This study indicated that pure Mg exhibited desirable degradation resistance in artificial saliva, which provided magnesiumbased materials with the potential to be used as esophageal stents.

Corrosion resistance of Zn-AI layered double hydroxide/ poly（lactic acid） composite coating on magnesium alloy AZ31

A Zn-AI layered double hydroxide （ZnAI-LDH） coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly（lactic acid） （PLA） coating was sealed on the top layer of the ZnAI-LDH coating using vacuum freeze-drying. The characteristics of the ZnAI-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy （EIS）. The results showed that the ZnAI-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAI-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.

Significantly improved photocatalysis-self-Fenton degradation performance over g-C3N4 via promoting Fe(Ⅲ)/Fe(Ⅱ)cycle

Photocatalysis-self-Fenton system,i.e.,photo-catalytic H_(2)O_(2)generation and utilization in situ for OH radials production to remove organic pollutants with high-fluent degradation and mineralization performance pos-sesses such advantages as cleanliness,efficiency and safety.However,its degradation activity always suffers from the Fe(Ⅲ)/Fe(Ⅱ)cycle.For this reason,graphitic carbon interface-modified g-C_(3)N_(4)(CUCN)was fabricated to remarkably improve photocatalysis-self-Fenton degra-dation activity.The experiment results indicated that CUCN-2%photocatalyst,in which the loading percentage of graphitic carbon was 2%,demonstrated the optimum degradation performance among all the counterparts.The mineralization degree for RhB in 3 h over CUCN-2%reached 63.77%,nearly 3.35-fold higher than the pristine g-C_(3)N_(4).The significantly improved mineralization efficiency was ascribed to the promoted Fe(Ⅲ)/Fe(Ⅱ)cycle by photogenerated electrons,which leading to the higher utilization efficiency of H_(2)O_(2)through Fenton reaction,thereby producing more hydroxyl radicals.It is anticipated that our work could provide new insights for the design of photocatalysis-self-Fenton system with exceptional degradation performance for actual photocat-alytic applications.

In vitro corrosion of Mg-Ca alloy- The influence of glucose content

Influence of glucose on corrosion of biomedical Mg-1.35Ca alloy was made using hydrogen evolution, pH and electrochemical polarization in isotonic saline solution. The corrosion morphologies, compositions and structures were probed by virtue of SEM, EDS, FTIR, XRD and XPS. Results indicate that the glucose accelerated the corrosion of the alloy. The elemental Ca has no visible effect on the corrosion mechanism of glucose for the Mg-1.35Ca alloy in comparison with pure Mg. In addition, the presence of CO2 has beneficial effect against corrosion due to the formation of a layer of carbonate- containing products.