Transfer of P1 inserts into a yeast-bacteria shuttle vector by co-transformation mediated homologous recombination

Manipulation of genomic inserts cloned into the bacteriophage P1 vector is hindered by the large size of the inserts. We have used co-transformation mediated recombination between the yeast-bacteria shuttle vector, pClasper, and various P1 clones to transfer the entire insert from the P1 into pClasper. This results in the insert being stably maintained in yeast, facilitating mutagenesis by homologous recombination. The recombinant plasmid can subsequently be transferred to and stably maintained in bacteria for efficient plasmid preparation. This method can also be applied to inserts from P1 artificial chromosome or bacterial artificial chromosome vectors.     

Luting composite thickness of two ceramic inlay systems

The objective of this study was to evaluate the effects of glass-ceramic inserts on reducing the marginal gaps caused by polymerization shrinkage in composite restorations. A light microscope was used to measure the largest gap at margins around restorations made in glass cylinders and tooth cavities with and without adhesion promoters. Where the cylinder was not silanated, the average gap was less in samples containing an insert than in those without. Two preparations were made in the dentin of 20 human molars. In each molar one cavity was restored with a dentin bonding agent and composite and the other with a dentin bonding agent and an insert seated in the composite. The average maximum gap width of restorations containing inserts was statistically less than for those with only composite (paired t-test, P<0.0001). When considering the volume of composite displaced by the insert, these results that the use of a glass-ceramic insert decreased the marginal gaps resulting form polymerization shrinkage.     

汽车发动机用无Co排气阀座圈材料的开发

烧结合金广泛地用于制作汽车发动机阀座圈（VSI）。就增高耐热与耐磨耗性能而言，在合金化设计上，烧结合金远比常规的锻钢与铸造合金灵活。特别足，一些高钻烧结材料由于耐磨耗与耐热性高而广泛用作排气阀座圈材料。鉴于近来将发动机的A／F比（空气／燃料比）调整到比常规的贫化（即空气／燃料比增高），排气阀座圈的工作环境趋于严酷。这种A／F比贫化的趋向旨在减少排出的废气和减低燃料消耗。另一方面。也需要不断地减少使用像钴之类环境负荷高的材料。同时，钴昂贵，减低钴含母有利于节省这些材料。这篇论文详细报道了无钴、无铅及有利于环境的排气阀座矧的开发与使用。     

Posterior cruciate supplementing total knee replacement using conforming inserts and cruciate recession. Effect on range of motion and radiolucent lines

This study was performed to determine if a sagittally curved conforming tibial insert can be used with a retained, but balanced, posterior cruciate ligament without deleterious effects on range of motion (ROM) and tibial radiolucencies, as compared with a flatter insert that is less conforming and does not require cruciate balancing. The authors reviewed 50 consecutive primary knees implanted with flatter posterior lipped inserts and 50 consecutive primary knees with curved inserts and posterior cruciate ligament balancing. The average ROM for both groups was the same postoperatively as preoperatively: 111 degrees for the posterior lipped inserts and 113 degrees for the curved inserts. The incidence of tibial radiolucent lines was 8% for both groups. The authors conclude that sagittally curved, more conforming tibial inserts with retained, but balanced, posterior cruciate ligaments, do not adversely effect ROM and tibial radiolucencies. Their use forms an attractive compromise between the schools of cruciate preservation and cruciate substitution, maximizing their advantages while minimizing their disadvantages. Functional ROM can be achieved while bone stock is preserved, the joint line is restored, and wear characteristics are improved.     

Space analysis: a comparison between sonic digitization (DigiGraph Workstation) and the digital caliper

The introduction of the DigiGraph Workstation permits the use of sonic digitization to measure lateral cephalometric values, mesiodistal tooth size and arch perimeter discrepancy as a one-stop diagnostic record taking set-up. This study compared the reproducibility of mesiodistal total tooth widths and arch perimeter values, on plaster casts, given by the DigiGraph Workstation and by digital calipers. Forty-seven sets of plaster casts of Southern Chinese children (mean age 12.5 years) comprised the sample. Arch perimeter was measured using calipers in six segments from the distal of the first permanent molar to its antimere in each arch. The total mesiodistal widths of all teeth, excluding second and third molars, were also measured. The difference between the available arch perimeter and the total tooth widths was taken as the arch perimeter discrepancy. Sonic digitization of the study casts was completed according to instructions of the DigiGraph software. Paired t-tests and F-tests were used to compare the two methods. Compared with manual measurement, there was an over-estimation of the total tooth widths by 1 mm in the mandible and 0.5 mm in the maxilla, and an arch perimeter discrepancy of 1.6 mm in the mandible and 0.4 mm in the maxilla when using the sonic method. The sonic digitization was not as reproducible as the digital caliper and its clinical usefulness in evaluating the space problem of an individual malocclusion should be interpreted with caution.     

Random removal of inserts from an RNA genome: selection against single-stranded RNA

We have monitored the evolution of insertions in two MS2 RNA regions of known secondary structure where coding pressure is negligible or absent. Base changes and shortening of the inserts proceed until the excessive nucleotides can be accommodated in the original structure. The stems of hairpins can be dramatically extended but the loops cannot, revealing natural selection against single-stranded RNA. The 3' end of the MS2 A-protein gene forms a small hairpin with an XbaI sequence in the loop. This site was used to insert XbaI fragments of various sizes. Phages produced by these MS2 cDNA clones were not wild type, nor had they retained the full insert. Instead, every revertant phage had trimmed the insert in a different way to leave a four- to seven-membered loop to the now extended stem. Similar results were obtained with inserts in the 5' untranslated region. The great number of different revertants obtained from a single starting mutant as well as sequence inspection of the crossover points suggest that the removal of redundant RNA occurs randomly. The only common feature among all revertants appears the potential to form a hairpin with a short loop, suggesting that single-stranded RNA negatively affects the viability of the phage. To test this hypothesis, we introduced XbaI fragments of 34 nucleotides that could form either a long stem with a small loop or a short stem with a large loop (26 nucleotides). The base-paired inserts were perfectly maintained for many generations, whereas the unpaired versions were quickly trimmed back to reduce the size of the loop. These data confirm that single-stranded RNA adversely affects phage fitness and is strongly selected against. The repair of the RNA genome that we describe here appears as the result of random recombination. Of the plethora of recombinants, only those able to adopt a base-paired structure survive. The frequency with which our inserts are removed seems higher than measured by others for small inserts in a reading frame in Q beta RNA. To account for this higher frequency, we suggest models in which the single-stranded nature of our inserts induces random recombination at the site of the insertion.     

The Coventry Award. Modular tibial insert micromotion. A concern with contemporary knee implants

This study investigates micromotion between modular tibial components, one of the causes of wear on the undersurface of polyethylene inserts. The authors measured motion at the interface of nine contemporary total knee implant designs by mechanically testing the implants in a servohydraulic testing machine. Anteroposterior and mediolateral motion between the tibial insert and baseplate were measured with an extensometer placed across the interface. These tests revealed that in all implants analyzed, sufficient motion occurred to create fretting at the modular interface. Although the testing configuration in this study was not a stimulation of in situ loading patterns, the authors observed hundreds of microns of motion even under a 100 N load and variability between implants of the same design, showing that there is room for improvement among locking mechanisms in modular total knee implants.     

Partitioned Distinct Element Method Simulation of Granular Flow within Industrial Silos

A method for performing discrete element simulations of granular flow and pressures within industrial silos is presented. Special attention is devoted to complex problems involving large numbers of particles and sophisticated boundary conditions due to the presence of inserts. The proposed method consists of partitioning the silo into layers that are analyzed sequentially, and in determining stresses and velocities at the virtual interlayer boundaries. The method is first validated by simulating the discharge of a single insert hopper containing 20,000 particles, performing both a simulation of the whole silo and a multilayer partition. The results show a small discrepancy in the displacement fields produced by the two simulations. Then the discharge of an industrial silo containing 170,000 particles with several inserts of different size and shape is simulated. The relevance of the stress and velocity fields obtained confirms the feasibility and the efficiency of the procedure. The method allows for managing huge numbers of particles with a limited memory capacity and a gain of computational time that may be significant depending on each particular case.     

Proteasome activation by REG molecules lacking homolog-specific inserts

The peptidase activities of eukaryotic proteasomes are markedly activated by the 11 S REG or PA28. The three identified REG subunits, designated alpha, beta, and gamma, differ significantly in sequence over a short span of 15-30 amino acids that we call homolog-specific inserts. These inserts were deleted from each REG to produce the mutant proteins REGalphaDeltai, REGbetaDeltai, and REGgammaDeltai. The purified recombinant proteins were then tested for their ability to oligomerize and activate the proteasome. Both REGalphaDeltai and REGgammaDeltai formed apparent heptamers and activated human red cell proteasomes to the same extent as their full-length counterparts. By contrast, REGbetaDeltai exhibited, at low protein concentrations, reduced proteasome activation when compared with the wild-type REGbeta protein. REGbetaDeltai was able to form hetero-oligomers with a single site, monomeric REGalpha mutant and with REGalphaDeltai. At low concentrations, the REGalphaDeltai/REGbetaDeltai hetero-oligomers stimulated the proteasome less than REGalpha/REGbeta oligomers formed from wild-type subunits, and the reduced activation by REGalphaDeltai/REGbetaDeltai was due to removal of the REGbeta insert, not the REGalpha insert. These studies demonstrate that the REGalpha and REGgamma inserts play virtually no role in oligomerization or in proteasome activation. By contrast, removal of REGbeta insert reduces binding of this subunit and REGalpha/REGbeta oligomers to proteasomes. On the whole, however, our findings show that REG inserts are not required for binding and activating the proteasome. We speculate that they serve to localize REG-proteasome complexes within cells, possibly by binding components in endoplasmic reticulum membranes.     

In vitro evaluation of marginal and internal adaptation of class II resin composite restorations after thermal and occlusal stressing

The aim of this in vitro trial was to evaluate the external and internal adaptation of class II composite restorations to tooth structure by means of replica scanning electron microscope (SEM) observation. Standard MOD preparations were cut in human extracted teeth with margins located above and below the cementoenamel junction. Cavities were restored with either a direct multilayered technique, inlays (using conventional or dual DBA application) or prepolymerized composite inserts, using similar restorative material (Syntac, Variolink and Tetric). Evaluations were performed after mechanical and thermocycling. For the marginal adaptation in enamel, the bevelled margins of the direct group resulted in higher percentages of "continuity" (92.5% mesially and 94.6% distally), while the "marginal tooth fracture" was the most commonly found defect in groups with a butt preparation (up to 29.4%, with inserts). For the marginal adaptation in dentin, "continuity" percentages varied from 59% (inlay) to 87.9% (insert). As regards the internal adaptation, results for the whole dentin interface varied from 43.1% (inlay) to 63.9% (inlay with dual bonding) of "continuity". No regional difference in internal adaptation was found between the different preparation areas, except between gingival dentin and gingival enamel (44.9% vs. 80.7% of continuity, all group pooled data). Debonding occurred only at the dentin-restoration interface and consistently took place at the top of the hybrid layer. In the present experimental conditions, the inlay or insert techniques, which make use of the Dual bonding concept, proved to have the best potential to maintain the integrity of dentin-restoration interface.     

Neonatal screening for the cystic fibrosis main mutation delta F508 in Estonia

When patients exhibit Class II defects requiring restoration, the treatment modality and respective preparation requirements may present challenges to the clinician. Aesthetics, chairside time, and expense become factors for the consideration of both dentist and patient. However, a new sonically driven system for the preparation and restoration of proximal defects was recently introduced (SONICSYS, Ivoclar Vivadent, Amherst, NY). This system, composed of diamond-coated tips and prefabricated ceramic inserts, promises to enable clinicians to efficiently, confidently, and expertly prepare and restore Class II defects in a timely, consistent, and cost-efficient manner. This article describes the components of the system and demonstrates its utilization in a case report.     

Confinement Effectiveness of FRP in Retrofitting Circular Concrete Columns under Simulated Seismic Load

The results of a research program that evaluated the confinement effectiveness of the type and the amount of fiber-reinforced polymer (FRP) used to retrofit circular concrete columns are presented. A total of 17 circular concrete columns were tested under combined lateral cyclic displacement excursions and constant axial load. It is demonstrated that a high axial load level has a detrimental effect and that a large aspect ratio has a positive effect on drift capacity. Compared with the performance of columns that are monotonically loaded until failure, three cycles of every displacement excursion significantly affect drift capacity. The energy dissipation capacity is controlled by FRP jacket confinement stiffness, especially under a high axial load level. The fracture strain of FRP material has no significant impact on the drift capacity of retrofitted circular concrete columns as long as the same confining pressure is provided, which differs from the common opinion that a larger FRP fracture strain is advantageous in seismic retrofitting. The amount of confining FRP greatly affects the length of the plastic hinge region and the drift capacity of FRP-retrofitted columns. A further increase in confinement after a critical value causes a reduction in the deformation capacity of the columns.     

Effect of Magnetic-Abrasive Treatment on Wear Resistance of Hard Alloy Inserts with Diffusion Coatings Based on TiC

The mechanism and effect of magnetic-abrasive treatment (MAT) on the wear resistance of WC ― 8 Co hard alloy inserts have been studied. MAT was carried out on hard alloy inserts before and after coating deposition. The results of local x-ray and electron microscopic analyses are discussed. It has been established that a TiC coating deposited by CVD after MAT contains iron inclusions. The transition layer (coating-hard alloy base) is narrower as compared with the literature data and contains more iron than the coating and base. The mechanism of the MAT effect on the wear resistance of inserts with diffusion coatings is proposed. The effect of MAT of insert coatings on their wear resistance is discussed as well. The highest level of strengthening has been achieved by treatment using the following scheme: magnetic-abrasive treatment + chemical vapor deposition + magnetic abrasive treatment (MAT + CVD + MAT).     

The restoration of destroyed crowns of the anterior teeth with combined inlays]

An original design of a microdenture insert is suggested, as are methods of preparing it to restore the frontal teeth after an injury not involving the pulp. The insert consists of two elements permitting disposition of the parapulpar pins at an almost right angle, providing a reliable fixation of the insert on the tooth. Clinical follow-up of 25 patients with 27 inserts for up to 3 years demonstrated the efficacy of such treatment.     

Specific excision of the inserted DNA segment from hybrid plasmids constructed by the poly(dA). poly (dT) method

The hybrid plasmid PBETAG, consisting of plasmid PMB9 DNA with an insert of rabbit globin DNA (about 600 base pairs) flanked by poly(dA) poly(dT) regions (Maniatis, T., Kee, S.G., Efstratiadis, A. and Kafatos, F.C. (1976) Cell 8, 163-182), was cleaved into two fragments by endonuclease S1 under conditions of partial denaturation. Only the smaller fragment (575 base pairs) contained globin-specific sequences, showing that excision had occurred in the A-T-rich regions. This method of cleavage provides a useful procedure for assessing the length of inserts in hybrid plasmids prepared by the poly(dA)-POLY(DT) tail method, and allows the preparative recovery of the insert.     

A nonradioactive method for improved restriction analysis and fingerprinting of large P1 artificial chromosome clones

The P1 artificial chromosome (PAC) cloning system is very useful for physical mapping, however, the large insert sizes cause difficulty in routine restriction analysis. In order to facilitate restriction mapping and fingerprinting, we have developed a simple, nonradioactive method for end-labeling and detection of restriction fragments from PAC clones. This method is very easy to implement, gives good differentiation of restriction fragments, and uses comparatively small amounts of DNA. We have used this method for restriction analysis of PAC clones containing inserts from human as well as from lower vertebrates. The method should also be applicable to other large-insert plasmid systems.