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.     

Silver Doped Magnesium Ferrite Nanoparticles: Physico-Chemical Characterization and Antibacterial Activity

Spinel phases, with unique and outstanding physical properties, are attracting a great deal of interest in many fields. In particular, MgFe₂O₄, a partially inverted spinel phase, could find applications in medicine thanks to the remarkable antibacterial properties attributed to the generation of reactive oxygen species. In this paper, undoped and Ag-doped MgFe_2-xAg_xO₄ (x = 0.1 and 0.3) nanoparticles were prepared using microwave-assisted combustion and sol–gel methods. X-ray powder diffraction, with Rietveld structural refinements combined with micro-Raman spectroscopy, allowed to determine sample purity and the inversion degree of the spinel, passing from about 0.4 to 0.7 when Ag was introduced as dopant. The results are discussed in view of the antibacterial activity towards Escherichia coli and Staphylococcus aureus, representative strains of Gram-negative and Gram-positive bacteria. The sol–gel particles were more efficient towards the chosen bacteria, possibly thanks to the nanometric sizes of metallic silver, which were well distributed in the powders and in the spinel phase, with respect to microwave ones, that, however, acquired antibacterial activity after thermal treatment, probably due to the nucleation of hematite, itself displaying well-known antibacterial properties and which could synergistically act with silver and spinel.     

The Domain and Microstructure of Resin-Bonded Magnets

This paper presents domain and structure studies of bonded magnets made from nanocrystalline Nd-(Fe, Co)-B powder. The structure studies were investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Mössbauer spectroscopy and X-ray diffractometry. On the basis of performed qualitative and quantitative phase composition studies, it was found that investigated alloy was mainly composed of Nd₂(Fe-Co)₁₄B hard magnetic phase (98 vol%) and a small amount of Nd_1.1Fe₄B₄ paramagnetic phase (2 vol%). The best fit of grain size distribution was achieved for the lognormal function. The mean grain size determined from transmission electron microscopy (TEM) images on the basis of grain size distribution and diffraction pattern using the Bragg equation was about ≈130 nm. HRTEM images showed that over-stoichiometric Nd was mainly distributed on the grain boundaries as a thin amorphous border of 2 nm in width. The domain structure was investigated using a scanning electron microscope and metallographic light microscope, respectively, by Bitter and Kerr methods, and by magnetic force microscopy. Domain structure studies revealed that the observed domain structure had a labyrinth shape, which is typically observed in magnets, where strong exchange interactions between grains are present. The analysis of the domain structure in different states of magnetization revealed the dynamics of the reversal magnetization process.     

过氧化氢溶液声学造影进行子宫输卵管通畅性检查的临床价值

目的：探讨超声下过氧化氢溶液声学造影对子宫输卵管通畅性的临床价值。方法选择2011年1月~2013年6月在河南省军区直属医院妇科收治的确诊为输卵管性不孕症的患者65例,按照入院顺序将其随机分为对照组和实验组,对照组32例(输卵管61条),其中3例为单侧输卵管切除,实验组33例(输卵管64条),其中2例单侧输卵管切除。对照组患者采用传统输卵管通液法进行诊断,实验组采用超声下3%过氧化氢造影法进行诊断,术后所有患者均采用泛影葡胺X线造影作为诊断标准,观察两组的诊断结果并分别与泛影葡胺X线下造影结果进行比较。结果对照组输卵管通畅44条,阻塞17条,采用泛影葡胺X线造影诊断输卵管通畅58条,阻塞3条,诊断结果比较,差异有统计学意义(字2=6.1,P<0.05);实验组输卵管通畅59条,阻塞5条,采用泛影葡胺X线造影诊断输卵管通畅62条,阻塞2条,诊断结果比较,差异无统计学意义(字2=3.6,P>0.05)。对照组诊断输卵管通畅符合率为72.13%,阻塞符合率为27.87%;实验组诊断输卵管通畅符合率为92.19%,阻塞符合率为7.81%;两组诊断符合率比较,差异有统计学意义(字2=7.45,P<0.05)。结论超声下过氧化氢溶液声学造影诊断子宫输卵管通畅情况方法操作简单,在诊治输卵管性不孕症方面具有临床价值,值得推广。     

周围型肺癌的MDCT影像特征分析

目的：探讨周围型肺癌的MDCT影像特征。方法回顾性分析本院经穿刺活检或手术病理证实的185例周围型肺癌临床及MDCT影像资料,从不同方位对肿瘤形态学特征、瘤肺界面和邻近改变、血管和支气管改变等方面进行分析研究。结果周围型肺癌的MDCT表现为院淤肿块形态有结节灶、肿块影及磨玻璃阴影;于肿瘤边缘可有分《征、毛刺征、胸膜凹陷征、血管征、支气管截断征;盂肿瘤内部有空泡征、空洞及钙化等。结论周围型肺癌的MDCT有其特征性影像表现,包括分《征、毛刺征、胸膜凹陷征及血管征等,是诊断周围型肺癌的关键。     

X线平片及螺旋CT在脊柱骨折中的诊断价值

目的：探讨X线平片及螺旋CT在脊柱骨折中的诊断价值。方法对本院2013年5月~2014年5月的120例脊柱骨折患者进行回顾性分析,随机分为实验组和对照组,各60例。实验组采用X线平片及螺旋CT进行诊断,对照组采用螺旋CT进行诊断。对诊断后的患者进行手术,术后观察两组的诊断情况。结果实验组的确诊率为98.3%,高于对照组的83.3%,差异有统计学意义（P<0.05）;实验组诊断出30例椎体内血肿、20例椎板骨折、9例骨折片突入椎管,漏诊率为1.7%,对照组诊断出25例椎体内血肿、15例椎板骨折、10例骨折片突入椎管,漏诊率为16.7%,两组漏诊率差异有统计学意义（字2=3.257,P<0.05）。结论采用X线平片及螺旋CT进行诊断,可以准确地诊断脊柱骨折,两者结合诊断的准确率更高,具有重要的临床意义,值得推广应用。     

双源双能量CT成像在新型冠状病毒肺炎中的应用价值

目的探讨双源双能量计算机体层成像（CT）不同单能量重建对新型冠状病毒肺炎（COVID-19）间质性病灶的显示和图像质量及辐射剂量的影响。 方法回顾性分析2020年1—3月郑州大学第一附属医院收治的20例COVID-19患者的胸部平扫影像学资料。比较同一患者双源双能量CT与常规CT的扫描辐射剂量。同时重建双源双能量CT扫描40、60、80、100、120 keV单能量图像,比较不同单能量图像间质性病灶的CT值和标准差（SD）,计算信噪比（SNR）和对比噪声比（CNR）;由2名经验丰富的肺部诊断医师采用5分法评估不同单能量图像质量,并进行比较。 结果双源双能量CT组的CT容积剂量指数（CTDI_vol）为（6.0±2.4）mGy,较常规CT组的（8.9±2.9）mGy下降了33%,且差异有统计学意义（t=10.694,P<0.001）;双源双能量CT组剂量长度乘积（DLP）和全身有效剂量（ED）分别为（217.5±79.6）mGy·cm和（3.1±1.1）mSv,低于常规CT组的（333.8±109.0）mGy·cm（t=10.727,P<0.001）和（4.67±1.52）mSv（t=10.730,P<0.001）。随着X线能量的升高,单能量图像的SNR和CNR逐渐增加,CT值和SD值逐渐降低,相邻两组间比较差异均有统计学意义（P<0.001）。2名诊断医师的图像质量主观评价一致性较好（Kappa值为0.700~0.857,P<0.001）,不同单能量图像主观评分差异均有统计学意义（P<0.001）,其中80 keV图像主观评分最高。 结论与常规CT相比,使用双源双能量CT降低了辐射剂量;120 keV单能量图像质量客观评价较高,但80 keV单能量图像更有利于间质性病灶的显示,对提示病情进展具有重要意义。     

肝包虫病与肝囊肿CT表现比较*

目的 探讨使用256排CT检查在鉴别肝包虫病与肝囊肿方面的临床价值。方法 2017年4月～2020年11月我院诊治的肝囊肿患者77例和肝包虫病患者34例接受256排CT增强扫描检查,采用ELISA法检测血清抗囊液抗原抗体(EgCF)、抗头节抗原抗体(EgP)、抗囊液半纯化抗原抗体(EgB)和抗泡球蚴抗体(Em2)。结果 本组肝包虫病患者术前血液嗜酸性粒细胞计数为(0.3±0.1)×10⁹/L,显著高于肝囊肿患者【(0.1±0.1)×10⁹/L,P＜0.05】;肝包虫病患者血清抗EgCF抗体和抗EgB抗体阳性率分别为85.3%和61.8%,均显著高于肝囊肿患者【分别为31.2%和0.0%,P＜0.05】;增强CT扫描,肝包虫病患者肝内存在类圆形、圆形或分叶状囊性灶,囊壁钙化;在入组的111例患者中,CT检查将3例(2.7%)肝包虫病误诊为肝囊肿,1例(1.0%)肝包虫病被误诊为肝转移癌,2例(1.8%)肝囊肿被误诊为肝包虫病。结论 CT检查能很好地显示肝包虫病囊性病灶的影像学特征,对鉴别肝包虫病与肝囊肿有帮助,为临床治疗提供可靠的影像学依据。     

Microleakage Analysis of Different Bulk-Filling Techniques for Class II Restorations: µ-CT,SEM and EDS Evaluations

This study aimed to compare two different bulk-filling techniques, evaluating the internal and external adaptation of class II resin-composite restorations, by analysing the gap formation using microcomputed tomography (µ-CT) and scanning electronic microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Two standardized mesio/disto-occlusal (MO/DO) cavities were prepared in eight extracted human third molars that were divided, according to the filling technique used, in the following two groups (n = 4): BG (Bulk&Go group) and BT (Bulk Traditional group). After universal bonding application, followed by the light curing, all teeth were restored using a bulk-fill composite. Specimens were scanned with µ-CT to evaluate 3D interfacial gaps. Acquired µ-CT data were analysed to quantify the gap formation. Complementary information to the µ-CT analysis were obtained by SEM. Thereafter, the chemical composition of tooth–restoration interface was analysed using EDS. The µ-CT analysis revealed gaps formation at the tooth–restoration interface for both the BG and BT groups, while within the restoration, only in the BT group there was evidence of microleakage formation. The scanning electron micrographs of both groups showed that the external marginal integrity of the restoration was preserved, while EDS showed the three different structures (tooth surface, adhesive layer and resin composite) of the tooth–restoration interface, highlighting the absence of gap formation. In both BG and BT, the two filling techniques did not show significant differences regarding the internal and external marginal adaptation of the restoration. To achieve a successful restoration, the clinician could be advised to restore a class II cavity using a single increment bulk-filling technique (BG), thus treating it as a class I cavity.     

X-ray Absorption (XRA): A New Technique for the Characterization of Granular Activated Carbons

The X-ray absorption (XRA) method using digital image processing techniques is a reliable technique to determine the exhaustion degree of granular activated carbons (GACs). Using an innovative digital image processing technique, the identification of individual adsorbed molecules or ions in a GAC was possible. Adsorption isotherm models (Langmuir and Freundlich) were used to simulate the adsorption equilibrium data of Methylene Blue (MB), nickel, cobalt and iodine. Freundlich equation was found to have the highest value of R² compared with Langmuir. The identification of distinctive patterns applying XRA for different adsorbed ions and molecules onto GAC was explored. It is demonstrated that unique XRA configurations for each adsorbed ion or molecule are found, as well as a proportional relationship between its incident energy (needed to achieve maximum photon attenuation) and the (effective) atomic number, the adsorbate mass and the molar or atomic mass of adsorbed molecule or ion. XRA method in combination with image histogram modifications was used to obtain a digital signature of adsorbed ions/molecules, giving distinct GSI values for each one in the used energy range. Probabilistic models prove that XRA results are within relationships between effective atomic number and photonic interaction probability, reinforcing the potentialities of XRA for monitoring (multi-)ion and/or molecule combinations on GAC using advanced digital image processing techniques. It was proved that the proposed approach could assess different adsorbed ions/molecules onto GACs in water purification systems.