Application of a thermodynamic nearest-neighbor model to estimate nucleic acid stability and optimize probe design: prediction of melting points of multiple mutations of apolipoprotein B-3500 and factor V with a hybridization probe genotyping assay on the LightCycler. (1/61)

BACKGROUND: PCR-based mutation detection is prone to methodological errors, e.g., in restriction length fragment polymorphism (RFLP) and allele-specific amplification (ASA), false PCR results may occur because of technical faults or atypical new mutations. METHODS: We investigated the ability of a genotyping assay based on hybridization of labeled oligonucleotides to detect and discriminate known and as yet unknown mutations in the factor V and apolipoprotein B-100 genes. Expected melting points were calculated using a nearest-neighbor model for nucleic acid duplex stability and compared with experimental findings derived from LightCycler melting curves. A method for genotyping the apolipoprotein B-100 G10699A and C10698T mutations is presented. RESULTS: All mismatches tested for in the probed sequence could be detected with a single probe. The measured melting points were in good agreement with their values predicted using the nearest-neighbor model (r = 0.96; y = 0.98x + 1.18; S(y|x) = 0.96; n = 24). CONCLUSIONS: This procedure not only allows the identification of the mutation of interest but also enables the discrimination from other potential mutations in the vicinity of the former. The nearest-neighbor model is valid for hybridization probe assays on the LightCycler and should be of general value in setting up such assays. We have shown for two clinically relevant genotyping examples that the LightCycler mutation detection system has superior discriminatory performance compared with conventional RFLP or ASA PCR-based methods for molecular diagnostic purposes. With this method, in every hybridization probe assay, all mutations under a properly designed probe should be detectable, but they will not necessarily be discriminated from each other in all cases.  (+info)

Phase transformations and age-hardening behaviors related to Au3Cu in Au-Cu-Pd alloys. (2/61)

Phase transformation behaviors in Au-Cu-Pd alloys were investigated by means of electrical resistivity measurements, hardness tests, X-ray diffraction and transmission electron microscopy. Anisothermal and isothermal annealing were performed. Two types of phase transformations were found, namely related to the single phase of Au3Cu and the coexistent phase of Au3Cu and AuCu I. The latter produced more remarkable hardening than the former. Hardening was brought about by the antiphase domain size effect of Au3Cu ordered phase in the single phase and by the formation of AuCu I ordered phase in the Au3Cu ordered matrix. There are three modes of phase transformation in the coexistent region depending on the composition. Each sequence is discussed.  (+info)

Phase transformation mechanisms in (AuCu)1-xPdx pseudobinary alloys by direct aging method. (3/61)

Phase transformation mechanisms in the AuCu-Pd pseudobinary system were studied by means of electrical resistivity measurements, hardness tests, X-ray diffraction and transmission electron microscopy. A direct aging method was employed to eliminate the otherwise unavoidable ordering that takes place rapidly during quenching into ice brine, hence it is important to distinguish the ordering processes with and without an incubation period. Three phase transformation modes occurred, namely; ordering at grain boundaries and in the grain interior with nucleation and growth mechanism after incubation, and spinodal ordering without any incubation period. The age-hardening of the alloys examined was attributed to AuCu I ordering. Nucleation and growth mechanism followed by twinning occurred in the specimens aged at higher temperatures, while spinodal ordering was seen in specimens aged in lower temperature. The spinodal ordering temperature of AuCu-Pd alloys increased according to Pd content.  (+info)

Isothermal age-hardening behaviour in a Au-1.6 wt% Ti alloy. (4/61)

This study describes research with a view to developing a new age-hardenable, high-carat dental gold alloy with better biocompatibility by addition of a small quantity of titanium to gold. The relationship between isothermal age-hardening and phase transformation of the Au-1.6 wt% Ti alloy was investigated by means of hardness testing, X-ray diffraction study, scanning electron microscopic observation and energy dispersive spectroscopy. The hardening in the initial stage of ageing seemed to be attributable to the continuous precipitation of the Au4Ti ordered phase in the supersaturated alpha solid solution matrix. The overaging with softening was attributed mainly to the formation of precipitates at the grain boundaries, which grew to bright lamellae and seemed to be composed of the Au4Ti phase.  (+info)

Relationship between Af temperature and load changes in Ni-Ti orthodontic wire under different thermomechanical conditions. (5/61)

Simple three point bending tests were performed on Ni-Ti wires with three different Af points (1 degree C, 13 degrees C and 34 degrees C) to clarify the relationship between Af temperature and load changes under constant deformation. Each wire was deformed at 37 degrees C and then thermal changes were imposed by temperatures of 2 degrees C or 60 degrees C. The load changes with thermal changes from 37 degrees C to 2 degrees C or 60 degrees C showed the same tendency on the wires with different Af points: In the loading stage, the load became lower than the initial level at 37 degrees C and in the unloading stage, the load became higher than the initial load. The largest load change in the unloading stage was measured with the 13 degrees C Af point wire. Care must be taken when handling Ni-Ti wire with an Af point of less than 1 degree C in order to prevent it from reaching the limit of critical stress of slip deformation when the temperature in the mouth rises to above 40 degrees C.  (+info)

Utility of Ni-Ti shape memory orthodontic wire. (6/61)

The characteristic temperature dependence of recovery force was evaluated for a Cu-containing Ni-Ti shape memory wire with the nominal Af point being 40 degrees C. It exerted mild recovery force within the range of the proposed optimum force at the usual oral temperature. Larger forces were generated when it was heated to temperatures above Af: 40, 50 or 60 degrees C. By subsequently cooling to temperatures below Af, the force decreased again, and vice versa. The excellent reversibility, reproducibility and durability of the recovery force were also confirmed. These results indicate that the shape memory wire may be a reasonable material for a new concept of intermittent orthodontic treatment, in which mild force will be applied to the tooth for most of the daily hours and the tooth movement will be intermittently accelerated by larger forces generated only when the patient has hot foods or drinks.  (+info)

Development of Ag-Pd-Au-Cu alloy for multiple dental applications. Part 1. Effects of Pd and Cu contents, and addition of Ga or Sn on physical properties and bond with ultra-low fusing ceramic. (7/61)

Ag-Pd-Au-Cu quaternary alloys consisting of 30-50% Ag, 20-40% Pd, 10-20% Cu and 20% Au (mother alloys) were prepared. Then 5% Sn or 5% Ga was added to the mother alloy compositions, and another two alloy systems (Sn-added alloys and Ga-added alloys) were also prepared. The bond between the prepared alloys and an ultra-low fusing ceramic as well as their physical properties such as the solidus point, liquidus point and the coefficient of thermal expansion were evaluated. The solidus point and liquidus point of the prepared alloys ranged from 802 degrees C to 1142 degrees C and from 931 degrees C to 1223 degrees C, respectively. The coefficient of thermal expansion ranged from 14.6 to 17.1 x 10(-6)/degrees C for the Sn- and Ga-added alloys. In most cases, the Pd and Cu contents significantly influenced the solidus point, liquidus point and coefficient of thermal expansion. All Sn- and Ga-added alloys showed high area fractions of retained ceramic (92.1-100%), while the mother alloy showed relatively low area fractions (82.3%) with a high standard deviation (20.5%). Based on the evaluated properties, six Sn-added alloys and four Ga-added alloys among the prepared alloys were suitable for the application of the tested ultra-low fusing ceramic.  (+info)

Reaction kinetics of solid-state cyclization of enalapril maleate investigated by isothermal FT-IR microscopic system. (8/61)

To investigate the reaction kinetics of the solid-state degradation process of enalapril maleate, a Fourier transform infrared microspectroscope equipped with thermal analyzer (thermal FT-IR microscopic system) was used. The isothermal stability study was conducted at 120-130 degrees C for 1-2 h and changes in the three-dimensional plots of the IR spectra of enalapril maleate with respect to heating time were observed. The study indicates that the bands at 1649, 1728, and 1751 cm(-1) assigned to intact enalapril maleate gradually reduced in peak intensity with heating time. However, the peak intensities at 1672 and 1738 cm(-1) (due to enalapril diketopiperazine (DKP) formation) and at 3250 cm(-1) (corresponding to water formation) gradually increased with heating time. The solid-state diketopiperazine formation and the degradation process of enalapril maleate via intramolecular cyclization were found to be simultaneous. The isothermal decomposition curves were sigmoidal and were characterized by induction and acceleration periods, indicating the presence of autocatalytic solid-state decompositions. Moreover, the power-law equation (n = 1/4) was found to provide the best fit to the kinetics of decomposition. This isothermal FT-IR microscopic system was easily used to investigate the degradation of enalapril maleate and the concomitant formation of DKP. The solid-state reaction of enalapril maleate required an activation energy of 195+/-12 kJ/mol to undergo the processes of decomposition and intramolecular cyclization.  (+info)