An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Powder Bed Fusion–Laser Beam (PBF–LB) processing of magnesium (Mg) alloys is gaining increasing attention due to the possibility of producing complex biodegradable implants for improved healing of large bone defects. However, the understanding of the correlation between the PBF–LB process parameters and the microstructure formed in Mg alloys remains limited. Thus, the purpose of this study was to enhance the understanding of the effect of the PBF–LB process parameters on the microstructure of Mg alloys by investigating the applicability of computational thermodynamic modelling and verifying the results experimentally. Thus, PBF–LB process parameters were optimized for a Mg WE43 alloy (Mg-Y_3.9wt%-Nd_3wt%-Zr_0.5wt%) on a commercially available machine. Two sets of process parameters successfully produced sample densities >99.4%. Thermodynamic computations based on the Calphad method were employed to predict the phases present in the processed material. Phases experimentally established for both processing parameters included α-Mg, Y₂O₃, Mg₃Nd, Mg₂₄Y₅ and hcp-Zr. Phases α-Mg, Mg₂₄Y₅ and hcp-Zr were also predicted by the calculations. In conclusion, the extent of the applicability of thermodynamic modeling was shown, and the understanding of the correlation between the PBF–LB process parameters and the formed microstructure was enhanced, thus increasing the viability of the PBF–LB process for Mg alloys.     

The birth and growth of neuroradiology in the USA

Summary Neuroradiology in the USA was started by the neurosurgeons Harvey Cushing, who personally made the first X-rays used to treat a patient with a neurological disability, and Walter Dandy, who first performed air ventriculography, ventriculoscopy, air encephalography and air myelography. The father of neuroradiology in the USA was Merrill Sosman, Cushing's associate. Modern neuroradiology was introduced into the USA from Europe by Mannie Schechter who was one of the original team of three Chief Editors of Neuroradiology.To commemorate the 50th anniversary of the founding of the Harvey Cushing Society (now called the American Association of Neurological Surgeons), and the completion of 10 years of publication of Neuroradiology     

Interspecies difference in liver-specific functions and biotransformation of testosterone of primary rat,porcine and human hepatocyte in an organotypical sandwich culture

Interspecies difference is an important issue in toxicology research. We compared the potential in vitro metabolism of human, porcine and rat hepatocytes over 2 weeks in culture in an organotypical culture model which reflects the in vivo situation. All three species show similar LDH-rates. Albumin measurements showed that rat cells are about twice as active as human and porcine hepatocytes. The ethoxyresorufin-O-deethylase (EROD) activity of the rat hepatocytes is with about 14 μU/10⁶ cells distinctly higher than those of porcine and human cells (1.8 and 0.5 μU/10⁶ cells respectively), furthermore, the activity of the rat EROD increases slightly during the prolonged time in culture, whereas those of porcine and human enzymes slightly decrease. Concerning ethoxycoumarin-O-deethylase (ECOD), the enzyme activities are found to be in three different ranges where rat cells show the highest activity with 66 μU/10⁶ cells, porcine hepatocytes exhibit an activity of about 23 μU/10⁶ cells, and human activity is lowest with 0.7 μU/10⁶ cells. All three species show a similar decreasing trend of ECOD during the period of study. Regarding the biotransformation of testosterone, human and porcine liver cells form three major metabolites whereas rat cells form a mixture of all measured metabolites. Hence, in vitro metabolism using porcine hepatocytes would be much more scientific sense than one using rat hepatocytes since the metabolic pathways are much closer to human metabolism.     

Hypoglycemic effect of Tournefortia hirsutissima L., on n-streptozotocin diabetic rats

The hypoglycemic effect of aqueous and butanolic extracts from Tournefortia hirsutissima (Boraginaceae) was determined on neonatal induced streptozotocin diabetic rats (n-STZ). Oral administration of water extracts at doses of 20 and 80mg/kg, and butanolic extracts (8 and 80mg/kg) significantly lowered the plasma glucose levels in diabetic rats within 3h. Glibenclamide was used as reference and showed similar hypoglycemic effect. Our results support the traditional use of the plant as a hypoglycemic agent; we observe a dose-dependent action of the extracts. HPLC analysis confirmed that the aqueous and butanolic extracts had the same chemical composition.     

Heterogeneity of human serum high-density lipoprotein (HDL 2 )

A technique is described for the detection of free fatty acids, triglycerides, wax esters and cholesterol esters on thin-layer Chromatographic plates. The fatty acids present in each fraction can be recovered from the plates after detection and quantitatively measured by gas-liquid chiomatography. This procedure has been sucessfully applied to the analysis of skin surface lipids.     

Evaluation of purified 4-deoxynivalenol (vomitoxin) for unscheduled DNA synthesis in the primary rat hepatocyte-DNA repair assay

Primary cultures of rat hepatocytes were used to determine unscheduled DNA synthesis (UDS) and cytotoxicity of purified 4-deoxynivalenol (vomitoxin), a trichothecene mycotoxin produced on cereal grains by fungi of the genus Fusarium. Nontoxic and toxic doses of deoxynivalenol, 0.1 to 1000 μg/ml, did not significantly increase UDS as measured by net grains per nucleus, net grains per nuclear area or percentage of cells incorporating 5, 6, 10 or 20 grains per nucleus. Evidence of cytotoxicity, manifested as a reduction in cell number in autoradiographs, pyknotic nuclei or vacuolated cytoplasm, was observed in hepatocytes treated with deoxynivalenol concentrations of 5 μg/ml and above. These findings suggest that the cellular toxicity of deoxynivalenol may not be mediated by a DNA-damaging event in cultured hepatocytes. An increased percentage of large-sized nuclei was also found to be associated with toxic doses of deoxynivalenol as well as 2-acetylaminofluorene used as the positive control.     

Comparison of the metabolic profiles of benzo[alpha]pyrene obtained from primary cell cultures and subcellular fractions derived from normal and methylcholanthrene-induced rat liver

Hepatocyte primary cell (HPC) cultures derived from either (a) non-induced (normal) or (b) methylcholanthrene (MC)-induced rat liver actively metabolized the carcinogen benzol[alpha]pyrene (BaP) over a 24-h period. In both cases, the BaP metabolites generated were qualitatively similar to those seen in the metabolism of BaP by isolated rat liver microsomal fractions; in addition, unidentified compounds were evident in the chromatographic profile generated by the cultured cells. In cells derived from (a), levels of known metabolites (phenols and diols) increased over the time period studied. On the other hand, in cells derived from (b), levels of diols decreased markedly after 8 h. These results suggest that induction with MC enhances both activation and, to a greater extent, conjugative-detoxification pathways of BaP, so that in cells obtained from (b) the formation of water-soluble metabolites is enhanced and levels of organic soluble metabolites are lower than in cells obtained from (a). Metabolism of BaP in primary cell culture derived from rat liver is thus seen to be similar to in vivo metabolism of the carcinogen, but somewhat in contrast to the in vitro microsomal (subcellular) metabolism of BaP where conjugative-detoxification pathways are virtually inoperative.     

Investigation of Micromechanical Properties and Tribological Behavior of WE43 Magnesium Alloy after Deep Cryogenic Treatment Combined with Precipitation Hardening

This study investigated the micromechanical and tribological properties of WE43 alloy (Mg-Y-Nd-Zr) alloy subjected to cryogenic treatment and precipitation hardening. Microindentation tests were carried out in the range of load from 100 to 1000 mN. The introduction of deep cryogenic treatment (DCT) was shown to increase hardness and Young’s modulus, and reduce the total indentation work. As the load set during the tests increased, a gradual decrease in the measured values was observed, indicating a significant relationship between the indent size and the value of the measured parameters. Cryogenic treatment used in conjunction with precipitation hardening (after solutioning and after aging) reduces the tribological wear of the alloy. Tests have shown an almost twofold reduction in the area of the wear trace and in the volumetric wear of the alloy, as well as a more than twofold reduction in linear wear, with relatively small fluctuations in the coefficient of friction. Abrasion was the main mechanism of wear. Areas where microcutting, adhesion and plastic deformation occurred were also observed. The results indicate the significant effectiveness of the applied heat treatment in improving the service life of the WE43 alloy containing rare earth metals.     

3 D MEDIC和3 D SPACE磁共振神经成像在腰骶丛神经根的一致性对比研究

目的 验证三维多回波数据联合成像 (three dimensional multi-echo data imagine combination with selective water excitation, 3D MEDIC WE)和三维快速自旋回波成像 (three dimensional sampling perfection with application optimized contrasts by using different flip angle evolution, 3D SPACE STIR) 序列在腰骶丛神经根成像中的可行性和重复性。方法 将55例受试者分为腰椎无异常表现的正常对照组(20例)、单纯性腰椎间盘突出症(lumbar disc herniation, LDH)组(20例)和慢性炎性脱髓鞘性多发性神经根神经病症(chronic inflammatory demyelinating polyradiculoneuropathy, CIDP)组(15例),分别应用两种腰骶丛神经根成像,评价图像质量参数信噪比(signal to noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)和对比度(contrast ratio,CR),并验证正常对照组、CIDP组和LDH组测量神经根直径的一致性。结果 两序列测得神经根直径的一致性较高(正常组r=0.95,CIDP组r=0.99,LDH组r=0.97,P<0.001),图像质量评价指标显示,3D SPACE STIR序列在SNR、CNR和CR三项指标中占优,3D MEDIC WE定性评估图像质量评分较高。两序列均能清晰显示正常腰骶丛神经根、病变所致的弥漫性形态增粗神经根以及间盘突出受挤压变形的神经根。结论 3D MEDIC WE和3D SPACE STIR序列可应用于腰骶丛神经根成像,两序列对正常和异常形态、走行的神经根评估具备很高的可行性和重复性。综合考量临床图像的定性、定量评价,可择优选择恰当的序列为腰骶丛神经根成像提供影像支持。