Edgewise Compressive Behavior of Composite Structural Insulated Panels with Magnesium Oxide Board Facings

Edgewise compression response of a composite structural insulated panel (CSIP) with magnesium oxide board facings was investigated. The discussed CSIP is a novel multifunctional sandwich panel introduced to the housing industry as a part of the wall, floor, and roof assemblies. The study aims to propose a computational tool for reliable prediction of failure modes of CSIPs subjected to concentric and eccentric axial loads. An advanced numerical model was proposed that includes geometrical and material nonlinearity as well as incorporates the material bimodularity effect to achieve accurate and versatile failure mode prediction capability. Laboratory tests on small-scale CSIP samples of three different slenderness ratios and full-scale panels loaded with three different eccentricity values were carried out, and the test data were compared with numerical results for validation. The finite element (FE) model successfully captured CSIP’s inelastic response in uniaxial compression and when flexural action was introduced by eccentric loads or buckling and predicted all failure modes correctly. The comprehensive validation showed that the proposed approach could be considered a robust and versatile aid in CSIP design.     

Linear Friction Welding of an AZ91 Magnesium Alloy and the Effect of Ca Additions on the Weld Characteristics

Solid-state welding offers distinct advantages for joining reactive materials, such as magnesium (Mg) and its alloys. This study investigates the effect of linear friction welding (LFW) on the microstructure and mechanical properties of cast AZ91 (Mg–9Al–1Zn) and AZ91–2Ca alloys, which (to the best knowledge of the authors) has not been reported in the literature. Using the same set of LFW process parameters, similar alloy joints—namely, AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca—were manufactured and found to exhibit integral bonding at the interface without defects, such as porosity, inclusions, and/or cracking. Microstructural examination of the AZ91/AZ91 joint revealed dissolution of the Al-rich second phase in the weld zone, while the Mn containing phases remained and were refined. In the AZ91–2Ca/AZ91–2Ca joint, the weld zone retained Ca- and Mn-rich phases, which were also refined due to the LFW process. In both joint types, extensive recrystallization occurred during LFW, as evidenced by the refinement of the grains from ~1000 µm in the base materials to roughly 2–6 µm in the weld zone. These microstructural changes in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints increased the hardness in the weld zone by 32%. The use of digital image correlation for strain mapping along the sample gage length during tensile testing revealed that the local strains were about 50% lower in the weld zone relative to the AZ91 and AZ91–2Ca base materials. This points to the higher strength of the weld zone in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints due to the fine grain size, second phase refinement, and strong basal texture. Final fracture during tensile loading of both joints occurred in the base materials.     

腺苷蛋氨酸联合门冬氨酸钾镁治疗小儿重度黄疸性肝炎疗效观察

目的：观察腺苷蛋氨酸联合门冬氨钾镁治疗小儿重度黄疸性肝炎的疗效。方法将210例小儿重度黄疸性肝炎患者随机分为观察组和对照组各105例。观察组采用腺苷蛋氨酸联合门冬氨钾镁治疗,对照组采用异甘草酸镁治疗,比较2组治疗效果。结果观察组的总有效率为94.3％高于对照组的83.8％,差异有统计学意义（P ﹤0.05）。治疗后观察组各临床症状改善情况优于对照组,差异有统计学意义（ P ﹤0.05）。2组患者接受治疗后均无严重不良反应发生。结论腺苷蛋氨酸联合门冬氨钾镁治疗小儿重度黄疸性肝炎能有效改善患者临床体征,疗效较好,不良反应少,值得临床推广。     

The Video Microscopy-Linked Electrochemical Cell: An Innovative Method to Improve Electrochemical Investigations of Biodegradable Metals

An innovative, miniature video-optical-electrochemical cell was developed and tested that allows for the conducting of electrochemical corrosion measurements and simultaneous microscopic observations over a small, well-defined surface area of corroding or degrading samples. The setup consisted of a miniature electrochemical cell that was clamped onto the metal sample and fixed under a video microscope before being filled with electrolyte. The miniature cell was comprised of afferent/efferent electrolyte ducts as well as a connection to the Mini Cell System (MCS) for electrochemical measurements. Consequently, all measured and induced currents and voltages referred to the same small area corroding completely within the field of view of the microscope, thus allowing for real-time observation and linking of surface phenomena such as hydrogen evolution and oxide deposition to electrochemical data. The experimental setup was tested on commercial purity (cp) and extra-high purity (XHP) magnesium (Mg) samples using open circuit potential and cyclic voltammetry methods under static and flowing conditions. The corrosion potential was shifted more anodically for cp Mg in comparison to XHP Mg under dynamic conditions. The corrosion current assessed from the cyclic voltametric curves were higher for the cp Mg in comparison to XHP Mg. However, there were no differences between static and flow conditions in the case of XHP Mg in contrast to cp Mg, where the current density was two times higher at dynamic conditions. The measurements and observations with this new method pave the way for a more detailed understanding of magnesium corrosion mechanisms, thus improving predictive power of electrochemical corrosion measurements on newly developed magnesium or other biodegradable alloys applied for medical devices. Different electrochemical tests can be run under various conditions, while being easy to set up and reproduce as well as being minimally destructive to the sample.     

MOC Doped with Graphene Nanoplatelets: The Influence of the Mixture Preparation Technology on Its Properties

The ongoing tendency to create environmentally friendly building materials is nowadays connected with the use of reactive magnesia-based composites. The aim of the presented research was to develop an ecologically sustainable composite material based on MOC (magnesium oxychloride cement) with excellent mechanical, chemical, and physical properties. The effect of the preparation procedure of MOC pastes doped with graphene nanoplatelets on their fresh and hardened properties was researched. One-step and two-step homogenization techniques were proposed as prospective tools for the production of MOC-based composites of advanced parameters. The conducted experiments and analyses covered X-ray fluorescence, scanning electron microscopy, energy-dispersive spectroscopy, high-resolution transmission electron microscopy, sorption analysis, X-ray diffraction, and optical microscopy. The viscosity of the fresh mixtures was monitored using a rotational viscometer. For the hardened composites, macro- and micro-structural parameters were measured together with the mechanical parameters. These tests were performed after 7 days and 14 days. The use of a carbon-based nanoadditive led to a significant drop in porosity, thus densifying the MOC matrix. Accordingly, the mechanical resistance was greatly improved by graphene nanoplatelets. The two-step homogenization procedure positively affected all researched functional parameters of the developed composites (e.g., the compressive strength increase of approximately 54% after 7 days, and 37% after 14 days, respectively) and can be recommended for the preparation of advanced functional materials reinforced with graphene.     

慢性腹泻患者结肠镜检查肠道准备方法的临床研究

目的探讨慢性腹泻患者在行结肠镜检查前的肠道准备方法。方法回顾性分析2017年3月-2018年3月行结肠镜检查的慢性腹泻患者,共119例。其中,37例患者(A组)于结肠镜检查前4 h开始口服复方聚乙二醇电解质散(PGEP)139.12 g(2 000 ml);42例患者(B组)于检查前4 h口服PGEP 208.68 g(3 000 ml);另外40例患者(C组)检查前4 h服用PGEP 104.34 g(1 500 ml),检查前2 h口服50.00%硫酸镁(MgSO_4)50 ml,再饮用温开水500 ml,至排泄液似清水样。应用Boston肠道准备量表(BBPS)评分,并对肠腔内气泡进行评分,比较3组患者肠道准备有效性、耐受性及安全性。结果 C组的进镜时间和退镜时间明显短于A组和B组;C组的BBPS评分明显高于A组和B组;C组的肠腔内气泡评分明显低于A组和B组;C组的肠道准备接受率、再次肠道准备接受率明显高于A组及B组;C组的总体不良反应评分明显低于A组及B组;差异均有统计学意义(P 0.05)。结论慢性腹泻患者采用PGEP联合MgSO_4进行结肠镜检查前肠道准备,其有效性、耐受性及安全性好。     

The Value of P Dispersion on Predicting Atrial Fibrillation After Coronary Artery Bypass Surgery; Effect of Magnesium on P Dispersion

Atrial fibrillation (AF) is a frequent arrhythmia complicating cardiac surgery, and generally occurs within the first week after surgery. Although there are some etiological mechanisms to explain the postoperative AF, the exact mechanisms of AF are not well clarified. In the present study, we would like to show the effect of MgSO₄ infusion on P duration and P dispersion, and its relation with AF complication in patients undergoing coronary artery bypass grafting. The patients were randomly allocated into two groups. Group A consisted of 93 patients to whom 1.5 g/day MgSO₄ infusion in 100 mL 0.9 NaCl solution (25 mL/hr) were applied the day before surgery, just after operation, and once daily for 4 days following surgery. Group B consisted of 55 control patients to whom 100 mL 0.9 NaCl solution (25 mL/hr) were applied at the same time points. Magnesium level was measured before the treatment and daily for the postoperative four days. As a result, AF developed in 2% of cases in group A, and in 36% of cases in group B (p < 0.001). Comparing the patients who developed AF, and who did not, no difference was detected with regard to baseline P max, P min, P dispersion and fourth day P min. But fourth day P max and P dispersion of patients who developed AF were significantly higher than who did not. Baseline Mg level were similar for those who developed AF, and who did not, but fourth day Mg level was significantly lower in AF group. As a result, our opinion that Mg infusion significantly decreased the incidence AF after cardiac bypass surgery was confirmed. And it's also clear that beneficial effect of MgSO₄ is associated with its decreasing effect on P dispersion.     

Beta-adrenergic stimulation of pig myocytes with decreased cytosolic free magnesium prolongs the action potential and enhances triggered activity

INTRODUCTION: Heart failure results in chronic beta-adrenergic stimulation, repolarization lability, and arrhythmias associated with early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs). Having described a significant reduction in intracellular free magnesium ([Mg2+]i) in experimental heart failure, we asked whether a reduction in [Mg2+]i would delay repolarization or facilitate EADs and/or DADs. METHODS AND RESULTS: Left ventricular myocytes were isolated from Yorkshire swine. Cytosolic free [Mg2+] was set at 0.12 mM (LoMg) or 1.2 mM (HiMg) through pipette dialysis. Action potentials (AP), Ca current (I(Ca)), and sodium/calcium exchange current (I(NCX)) were measured in the presence or absence of isoproterenol (2 microM) at 37 degrees C. Under basal conditions (0.1-Hz stimulation, 2 mM external [Ca2+]), reducing [Mg2+]i had no effect on AP duration and I(Ca) but did significantly enhance I(NCX). In contrast, during superfusion with isoproterenol, reduced [Mg2+]i caused a significant increase in AP duration at both 50% and 90% repolarization (APD50 and APD90) compared with HiMg (P < 0.05). LoMg cells manifested a high incidence of triggered activities, including spontaneous AP, EADs, and DADs (83.3% in LoMg, n = 12 vs 38.3% in HiMg, n = 13; P < 0.05). I(Ca) and I(NCX) were significantly increased in LoMg cells compared with HiMg cells (P < 0.05). CONCLUSION: Decreased cytosolic free magnesium prolongs AP duration and increases the incidence of triggered activity during beta-adrenergic stimulation. These effects may be due to increased I(Ca) and I(NCX) in the presence of reduced intracellular [Mg2+]. A magnesium-dependent increase in triggered activity coupled with delayed repolarization during beta-adrenergic stimulation could contribute to the arrhythmogenic substrate in heart failure.     

包头地区918例儿童不同年龄阶段4种矿物质元素水平变化趋势及差异性比较

目的 了解包头地区0～12岁不同年龄段儿童全血中锌、铁、镁、铜4种矿物质元素营养水平及变化趋势。方法 0~12岁健康体检的儿童中随机抽样918例, 利用SPSS 16.0软件包进行统计分析。结果 4个年龄阶段Zn、Fe均有较高的缺乏率;随年龄的增长, 锌元素水平逐渐增加, 铁元素水平整体呈上升趋势, 6岁后上升更加明显;Cu和Mg元素缺乏率较低;镁元素水平随年龄增长呈上升趋势; 0～6岁间儿童体内铜元素的水平变化不明显, 6岁后含量明显下降。结论 包头地区儿童4种矿物质元素的缺乏顺位依次为:锌、铁、铜、镁;儿童4种矿物质元素诊断标准应按年龄阶段划分。     

硫酸镁联合西地那非治疗新生儿持续性肺动脉高压的临床观察

目的：探讨硫酸镁联合西地那非治疗新生儿持续性肺动脉高压（PPHN）的疗效及其对患儿血氧饱和度和不良反应的影响。方法：选择我院新生儿重症监护室收治的新生儿持续性肺动脉高压患儿64例,随机分为观察组和对照组各32例。两组患儿均给予PPHN常规治疗,对照组采用西地那非,观察组采用西地那非+硫酸镁,根据患儿自身状况调整用药时间,连续治疗3~5 d,比较两组患儿的近期疗效及治疗前、治疗72 h后肺动脉压力（PAP）、氧动脉分压（PaO2）、二氧化碳分压（PaCO2）及血氧饱和度（SaO2）,记录治疗期间药物不良反应。结果：治疗后观察组总有效率90.63%,高于对照组的78.13%（P<0.05）;治疗后观察组PAP、PaO2、PaCO2、SaO2较对照组改善更明显（P<0.05）;观察组不良反应发生率9.36%,低于对照组的18.76%（P>0.05）。结论：西地那非和西地那非联合硫酸镁均可治疗新生儿持续性肺动脉高压,其中联合用药可在不增加不良反应情况下可达到更好的治疗效果,且能明显提高患儿血氧饱和度。