Characterization of damage modes in dental ceramic bilayer structures

Results of contact tests using spherical indenters on flat ceramic coating layers bonded to compliant substrates are reported for selected dental ceramics. Critical loads to produce various damage modes, cone cracking, and quasiplasticity at the top surfaces and radial cracking at the lower (inner) surfaces are measured as a function of ceramic-layer thickness. It is proposed that these damage modes, especially radial cracking, are directly relevant to the failure of all-ceramic dental crowns. The critical load data are analyzed with the use of explicit fracture-mechanics relations, expressible in terms of routinely measurable material parameters (elastic modulus, strength, toughness, hardness) and essential geometrical variables (layer thickness, contact radius). The utility of such analyses in the design of ceramic/substrate bilayer systems for optimal resistance to lifetime-threatening damage is discussed.     

2,8-Dihydroxyadenine urolithiasis in a patient with considerable residual adenine phosphoribosyltransferase activity in cell extracts but with mutations in both copies of APRT

We have examined the mutational basis of adenine phosphoribosyltransferase (APRT, EC 2.4.2.7) deficiency (MIM 102600) in a patient of Polish origin who has been passing 2,8-dihydroxyadenine (DHA) stones since birth, but has considerable residual enzyme activity in lymphocyte extracts. The five exons and flanking regions of APRT were amplified by PCR and then sequenced. A single T insertion was identified at the intron 4 splice donor site (TGgtaa to TGgttaa:IVS4+2insT) in one allele from the proband, his mother, and brother. A G-to-T transversion in exon 5 (GTC-to-TTC:c.448G>T, V150F) was identified in the other allele, and this mutation was also present in one allele from the father and the paternal grandmother. Tru91 and AvaII digestions of PCR products spanning exons 4 and 5, respectively, confirmed the mutations. The mother was heterozygous for an intragenic TaqI site, but all other family members were homozygous for the presence of this site. IVS4+2insT, located on the allele containing the TaqI site, has been identified previously in several families from Europe, suggesting a founder effect, but the substitution in exon 5 is a novel mutation. IVS4+2insT is known to result in complete loss of enzyme activity, and our results suggest that V150F produces an enzyme that is nonfunctional in vivo but has considerable residual activity in vitro.     

Production and Characterization of Generic Antibodies Against s-Triazine and Sulfonylurea Herbicides

Two different hapten designs have been suggested for production of generic antibodies. The first approach was based on the immunogen prepared by conjugating simazine mimic to carrier proteins through the Cl position of the s-triazine herbicide. For sulfonylurea herbicides a single ring hapten strategy was designed in order to produce antibodies with dominant selectivity towards arylsulfonyl or triazine moieties of metsulfuron-methyl. The best monoclonal antibody raised against simazine-derived hapten mimic (clone B10/B8/D2) exhibited in direct ELISA a broad pattern for a group of methylthio and methoxy s-triazines. Cross-reactivities based on simazine ( = 100%) were 417, 125, 25, 50, 28, 42 and 11% for simetryn, ametryn, prometryn, terbutryn, aziprotryn, atraton and atrazine, respectively. The superiour generic pattern was found for monoclonal antibody raised against s-triazine moiety of metsulfuron-methyl herbicide (clone 2C8/C8). This antibody showed in indirect ELISA the cross-reactivity values 100, 142, 95, 60, 40, 167, 83 and 21% for metsulfuronmethyl, cinosulfuron, triasulfuron, primisulfuron-methyl, thifensulfuron-methyl, chlorsulfuron and prosulfuron and tribenuron-methyl, respectively. The assays using both monoclonal and polyclonal antibodies operated within the ppt-ppb calibration ranges.     

Preparation of graded porous titanium coatings on titanium implant materials by plasma spraying

Graded porous titanium coatings have been deposited on titanium substrates for dental implants by plasma spraying in an argon atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness measurement, and tensile strength tests were performed on graded porous coatings. The results showed that Ti(3)O(5) was formed in the outermost surface of the porous coatings due to oxidation. The graded porous coatings consisted of three layers. The outer layer was full of macropores with a surface roughness of approximately 100 microm. The diameter of many macropores reached and even surpassed 150 microm, which could be beneficial for tissue to grow into the coating. The middle layer consisted of a mixture of micropores and macropores. The inner layer was a very dense and tight interface layer that included mechanical, physical, and metallurgical bonding. In tensile strength tests, testing bars peeled off the coatings, because the adhesive agent fractured, but the coatings remained intact.     

200MHz的H面号角环形相控阵系统热疗深部肿瘤的研究

本文提出并研究了一种新型的电磁热疗系统-H面号角环形相控阵系统。推导出了适应性广的理论公式。以肺部CT图为模型,用矩量法计算得到了胸腔横断面内电场分布及吸收功率分布的计算机数值结果。结果表明,在200MHz的电磁波辐射下,适当调节阵列各单元的相位,振幅和位置,肺部肿瘤可得到优化的选择性加热,从而达到最佳的热疗效果。     

Present status of study on reversion of anti-leukemic multidrug resistance

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