Image layer characteristics of the PC 1000 (mark II)

The objective of this study was to investigate empirically the image layer characteristics of the PC 1000 Mark II. Radiographs were taken of a lead resolution grid positioned at 1 mm increments along angular intervals of the projected x-ray beam. The receptor was T-Mat G film combined with Lanex Regular Screens. The path of the effective rotation center was determined using a film positioned horizontally at right angles to the slit beam. The vertical magnification factor, horizontal magnification and Distortion Index, corrected for the position of the tomographic layer, were calculated using a reference object placed at various resolution limits of the image layer. The beam projection angle was compared to the average dental arch shape and proximal contact angle. The maximum resolution observed at the central plane of the image layer was 4 lp · mm⁻¹. The image layer width at the 1.5 lp · mm⁻¹ resolution contour varied from 12 mm anteriorly to 41 mm posteriorly. The vertical magnification factor within the image layer showed a linear increase along the beam path from 1.21 to 1.36. The horizontal magnification varied from 1.07 to 1.71, and the Distortion Index from 0.85 to 1.15. The beam projection angulations to the average arch shape ranged from 90° anteriorly to 115° in the premolar segments and 105° in the molar regions. The empirically derived image layer of the PC 1000 Mark II conforms to the shape of the average dental arch and that found using MTF analysis. The spatial resolution attained using a standard receptor is within the acceptable range.     

Voltammetric lability of multiligand complexes: the case of ML2

The voltammetric lability of a complex system, where a metal ion M and a ligand L form the species ML and ML₂, is examined. Together with the rigorous numerical simulation of the problem, two limiting cases are analysed for the overall process ML₂ → M: (i) the most common case for aqueous complexes, where ML → M is the kinetically limiting step and (ii) the case where ML₂ → ML is limiting. In both cases, analytical expressions for the lability criteria are provided which show good agreement with the results obtained from the rigorous numerical simulation of the problem.     

Qualitative analysis of the removal of the smear layer in the apical third of curved roots: conventional irrigation versus activation systems

Introduction

The aim of this study was to evaluate the effectiveness of different irrigant agitation techniques on smear layer removal in curved root canals.

Methods

Mesiobuccal canals of 62 extracted lower molars with a curvature of 33 degrees were used and instrumented up to ProTaper F2. The samples were divided into 3 experimental groups according to the final irrigation: conventional irrigation, ultrasonic irrigation, and sonic irrigation by using the EndoActivator system. The control group was composed of 2 specimens without any final irrigation. In all of the experimental groups, 5 mL of 17% ethylenediaminetetraacetic acid was used for 1 minute, and 5 mL of 2.5% NaOCl was used for 30 seconds. The analysis of the apical region was performed via scanning electron microscopy by 3 examiners. The data were submitted to the Kruskal-Wallis and Dunn tests (P < .05).

Results

The activation systems removed significantly more smear layer than did conventional irrigation.

Conclusions

Sonic and ultrasonic irrigation resulted in better removal of the smear layer in the apical third of curved root canals than did conventional irrigation.     

人工智能对基层影像医生筛查肺结节的辅助价值

目的探讨基层影像医生结合人工智能辅助诊断系统对厚层CT中4 mm以上结节检出效能的差异。方法前瞻性收集2019年1月1日至1月31日在我院接受常规胸部CT检查的118例患者并进行层厚5 mm骨算法重建,由两位十年以上诊断经验的主治医师和一位十五年以上诊断经验的副主任医师借助人工智能软件(InferRead CT_Lung 6.0,Infervision,Beijing,推想科技)确定肺结节金标准。由基层医院两位主治医师对CT图像进行独立阅片,记录结节的数量、位置、长径和标记时间,两周后再次借助AI对同一批图像进行阅片,计算医生独立阅片(A组)及借助AI(B组)两种情况下的结节检测敏感度、假阳性率,同时比较两种情况标记时间。结果A组和B组对于4 mm以上肺结节检出总数分别为172和293个,其中真阳性结节数分别为112和171个,假阳性结节数分别为60和122个。B组肺结节的检测敏感度显著高于A组(P0.01)。A、B两组医生肺结节平均检测时间比较,差异有统计学意义(P0.05)。结论 AI对于肺结节检出具有较好的辅助能力,借助AI辅助诊断系统的基层影像医生对厚层图像4 mm以上肺结节的标记时间更短,结节诊断敏感度更高。     

基于网络平台的中医统计学混合教学模式探索与实践

目的:在中医统计学教学过程中构建混合式教学框架并探索其应用效果。方法:构建高度契合中医类专业医学统计学教学的混合教学框架。选取河北中医学院9个专业2252名学生作为研究对象,课程结束对教学效果进行评估。结果:学生对统计学基本方法的理解及课程的学习热情均有提高。结论:混合教学模式可显著提高中医院校医学统计学教学效果。     

桃红四物汤醇提液的薄层分离与定性鉴别

目的：桃红四物汤醇提液的薄层分离与定性鉴别。方法：采用薄层色谱法,选用硅胶G 薄层板,以正丁醇- 冰乙酸- 水（4∶1.5∶5,上层）为展开剂,置紫外灯（365 nm）下检视,观察桃红四物汤醇提液中化学成分的展开情况,再选用碘蒸气对各斑点进行显色,并将薄层板置于薄层扫描仪进行扫描,记录各斑点的吸收光谱图与比移值,与对照品进行观察对比。结果：桃红四物汤醇提液共分离得到5 个斑点,其中定性鉴别出3 个斑点,分别为来自红花的羟基红花黄色素A、来自白芍的芍药苷、来自当归和川芎的阿魏酸;其它2 个斑点在组成桃红四物汤的六个单味药中均未检出。结论：薄层色谱法能实现对桃红四物汤醇提液中化学成分的分离,可在此基础上进一步进行新成分的确定,分离方法简单快速、稳定可行。     

Randomised double-masked placebo-controlled trial of the cumulative treatment efficacy profile of intense pulsed light therapy for meibomian gland dysfunction

PurposeTo assess long-term cumulative treatment effects of intense pulsed light (IPL) therapy in meibomian gland dysfunction (MGD).MethodsEighty-seven symptomatic participants (58 female, mean ± SD age, 53 ± 16 years) with clinical signs of MGD were enrolled in a prospective, double-masked, parallel-group, randomised, placebo-controlled trial. Participants were randomised to receive either four or five homogeneously sequenced light pulses or placebo treatment to both eyes, (E-Eye Intense Regulated Pulsed Light, E-Swin, France). Visual acuity, dry eye symptomology, tear film parameters, and ocular surface characteristics were assessed immediately before treatment on days 0, 15, 45, 75, and four weeks after treatment course completion on day 105. Inflammatory and goblet cell function marker expression, and eyelid swab microbiology cultures were evaluated at baseline and day 105.ResultsSignificant decreases in OSDI, SPEED, and SANDE symptomology scores, and meibomian gland capping, accompanied by increased tear film lipid layer thickness, and inhibited Corynebacterium macginleyi growth were observed in both treatment groups (all p < 0.05). Sustained clinical improvements occurred in both treatment groups from day 75, although significant changes from day 45, in lipid layer quality, meibomian gland capping, OSDI and SANDE symptomology, were limited to the five-flash group (all p < 0.05).ConclusionsIPL therapy effected significant improvements in dry eye symptomology, tear film lipid layer thickness, and meibomian gland capping in MGD patients. Five-flash IPL treatment showed superior clinical efficacy to four-flash, and an initial course of at least four treatments is suggested to allow for establishment of sustained cumulative therapeutic benefits prior to evaluation of overall treatment efficacy.Trial registration numberACTRN12616000667415.     

Evaluation of use of essential fatty acids in topical ophthalmic preparations for dry eye

PurposeEssential fatty acids (EFAs) as dietary supplements are used in treating dry-eye for reducing inflammation at the ocular surface. Their topical application in eye drops to deliver fatty acid (FA) directly to the ocular surface requires thorough investigation. Being lipids in nature EFAs can interact with tear lipids and affect tear stability. This study aimed at investigating the biophysical interactions of EFAs with Meibomian lipids.MethodsRheology of mixtures of Human Meibomian lipids with EFAs (LA-linoleic acid, ALA-alpha-linolenic acid), OA (oleic acid), and GLA (gamma-linolenic acid) was studied using Langmuir trough technology on an artificial tear solution at the ocular surface temperature. Pressure-area profiles were used to determine compressibility and elasticity of the mixed films.ResultsLA enhanced spreading of Meibomian lipids and increased their compressibility and elasticity which can be beneficial for tear stability. ALA condensed Meibomian lipids film with less elasticity deemed unfavourable for tear stability. OA expanded Meibomian lipids but decreased elasticity at high compressions making films less stable. GLA had little or no favourable effect on tear stability. Higher concentrations of FAs made films less stable.ConclusionsEFAs or OA in topical ophthalmic preparations can affect spread and stability of the tear film lipid layer. Rheology of mixed films should be tested using Langmuir trough technology to determine suitable type and amount of a lipid additive for therapeutic eye drops. In topical applications, the omega-6 LA (not omega-3 FA) at low concentrations (20 mol%) can be beneficial for enhancing tear stability in dry eye patients.     

弱视患者发病机制及眼部结构的研究进展

弱视是一种儿童视觉发育关键期常见的眼科疾病,其发病机制复杂。传统观念认为弱视不会出现明显眼球器质性改变,但近年随着研究的深入,研究者们发现弱视患者不仅脑部解剖存在差异,在眼部结构也与正常人不尽相同,这为探索弱视发病机制提供了新的思路。本文就弱视患者的发病机制及眼部结构改变进行了总结,从发病机制、脉络膜厚度(CT)、眼部血管面积及密度、视网膜神经纤维层(RNFL)厚度以及弱视患者遮盖治疗后的眼部结构改变等方面进行综述。     

糖尿病视网膜病变患者泪膜脂质层厚度与黄斑微血管改变的相关性

目的:分析糖尿病视网膜病变患者泪膜脂质层厚度(LLT)与黄斑区微血管结构参数的相关性。方法:选取2018-01/12于我院确诊的2型糖尿病合并非增生期(NPDR组)和增生期(PDR组)糖尿病视网膜病变患者各60例60眼,另选取年龄、性别相匹配的健康志愿者60例60眼作为正常对照组。三组受检者均经Lipiview眼表面干涉仪检查LLT,OCT血流成像仪(OCTA)检查黄斑无血管区面积(FAZ)、视网膜浅层毛细血管层(SCL)和视网膜深层毛细血管层(DCL)血管密度,比较各参数之间的差异和相关性。结果:正常对照组受检者LLT(69.87±11.401nm)高于NPDR(54.87±7.453nm)和PDR组(42.67±5.246nm),FAZ(0.312±0.021mm^2)小于NDPR组(0.389±0.037mm^2)和PDR组(0.437±0.032mm^2),SCL血管密度(51.977%±4.164%)显著高于NPDR(47.067%±4.757%)和PDR组(41.865%±5.512%),DCL血管密度(49.578%±2.619%)高于NPDR组(46.032%±2.622%)和PDR组(40.598%±2.671%)(均P<0.01)。正常受检者LLT与FAZ、SCL和DCL血管密度无相关性;NPDR组和PDR组患者LLT与FAZ均呈负相关关系(r=-0.922、-0.923,均P<0.01),与SCL血管密度均呈正相关关系(r=0.798、0.902,均P<0.01),与DCL血管密度均无相关性(r=0.140、0.073,P=0.285、0.581)。结论:糖尿病视网膜病变患者泪膜脂质层厚度降低,泪膜稳定性下降,并与黄斑微血管结构改变存在相关关系。