Low Exponent Values Research Articles

The effects of dehiscence and fenestration before orthodontic treatment on external apical root resorption in maxillary incisors

The objective of this study was to investigate the effects of dehiscence and fenestration on external apical root resorption (EARR) in maxillary incisors. Seventy-eight patients were selected for this study. We set dehiscence, fenestration, sex, extraction, or nonextraction, tooth position, initial age, and duration of treatment as independent variables and EARR as the dependent variable. General statistical descriptions for these variables were made by mean, standard deviation and occurrence rates, etc. To make the data visualization and find more information, 2 heat maps were made. Generalized estimation equation analysis was performed to determine associations between EARR and independent variables. The occurrence rates of dehiscence and fenestration in maxillary incisors were 14.77% and 10.74%, respectively. The average value of EARR was 1.09±0.87mm in this study. Dehiscence, tooth position, extraction, initial age, and duration had significant correlations with EARR. The ratio of exponent B was 1:1.643 for dehiscence and nondehiscence, whereas fenestration and sex had no significant association with EARR. The amount of EARR at maxillary incisors in patients with dehiscence before orthodontic treatment might be less than that in patients without it, and different incisors might have different contributions to it. However, the low value of exponent B for dehiscence meant that there might be other unknown factors that were involved in this study.

Effect of temperature on grain growth kinetics of high strength Ti–2Al–9.2Mo–2Fe alloy

Abstract Grain growth behaviors of a beta titanium alloy (Ti–2Al–9.2Mo–2Fe) have been systematically investigated for various temperatures. Quantitative evaluations of the grain growth kinetics over a wide range of temperatures from 820 °C to 1000 °C have been performed. The results showed that the isothermal grain growth kinetics followed the normal growth behavior. The solution-treated alloy at lower temperatures (820–900 °C) exhibited a good uniformity of the grain size. It showed a poor uniformity of the grain size due to the abnormal grain growth at higher temperatures (950–1000 °C). The grain growth exponent values ( n ) were at the range of 0.1–0.2, about 0.1 at lower temperatures and about 0.2 at higher temperatures. They were lower than other beta titanium alloys. The lower exponent values ( n ) and the higher activation energy ( Q ) can be attributed to the solute drag effect and the high Mo content with low diffusivity in Ti matrix.

Characterization of polysaccharide–protein complexes by size-exclusion chromatography combined with three detectors

Two water-soluble samples (TM1 and TM2) were extracted from Pleurotus tuber-regium using 0.9% aqueous NaCl at 20 and 80 °C to obtain relatively low molecular mass fractions. The chemical structure of TM1 was analyzed to be a branched heteropolysaccharide–protein complex, and the sugar moiety was mainly β-(1→6)-, β-(1→4)-, and β-(1→3)-linked glucan containing galactose and mannose. TM2 was a branched polysaccharide–protein complex, and the sugar moiety was mainly β-(1→6)-, β-(1→4)-, and β-(1→3)-linked glucan. Preparative size-exclusion chromatography (SEC) and analytical SEC combined with three detectors were used to detect the TM1 and TM2 samples, confirming that the proteins were bonded to the polysaccharides. Furthermore, analytical SEC combined with online laser light scattering, differential refractive index detector, and UV to determine the components, weight-average molecular mass ( M w) and chain conformation of the samples. The relatively low exponent values ( ν) of 〈 S 2 〉 z 1 / 2 = k ν M w ν for the samples in 0.15 M aqueous NaCl at 25 °C suggested that TM1 and TM2 existed in compact sphere conformation in the aqueous solution. This work provided valuable information on the structure and chain conformation characterization of the polysaccharide–protein complex having relatively low M w.

Impedance analysis of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 ceramic

0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 ceramic was prepared by citrate gel method. The electrical property of this compound was investigated using impedance spectroscopy. The appearance of grain and grain boundary is evident at higher temperature (≥425°C). The depression of semicircle in the impedance plot and the value of full width half maximum (FWHM) of the peaks in the modulus plot show that the compound exhibits non-Debye relaxation process. The impedance analysis further provided the value of relaxation frequency, which is a characteristic intrinsic property of the material. The temperature variation of the bulk conductivity indicated an Arrhenius type of thermally activated process, showing a linear variation upto 425°C and above which it is dominated by grain boundary conduction, which was evident from the slope change at 425°C. The temperature coefficients of the resistance (α) were derived being equal to −1.4×10−2C−2 at 400°C. The low value of exponent (s) indicates the presence of asymmetric charge defects.

Exact solutions for models of evolving networks with addition and deletion of nodes

There has been considerable recent interest in the properties of networks, such as citation networks and the worldwide web, that grow by the addition of vertices, and a number of simple solvable models of network growth have been studied. In the real world, however, many networks, including the web, not only add vertices but also lose them. Here we formulate models of the time evolution of such networks and give exact solutions for a number of cases of particular interest. For the case of net growth and so-called preferential attachment--in which newly appearing vertices attach to previously existing ones in proportion to vertex degree--we show that the resulting networks have power-law degree distributions, but with an exponent that diverges as the growth rate vanishes. We conjecture that the low exponent values observed in real-world networks are thus the result of vigorous growth in which the rate of addition of vertices far exceeds the rate of removal. Were growth to slow in the future--for instance, in a more mature future version of the web--we would expect to see exponents increase, potentially without bound.

The effect of octyl glucoside on rheological behavior of diluted and concentrated lamellar phases

We have investigated the rheological properties of lamellar liquid crystal formed by nonionic surfactants at low and high surfactant concentrations with a small amount of octyl glucoside and their relationship with the topology of the bilayer. Rheology is a specific signature of each bilayer topology. The decrease in viscosity by increasing the shear rate according to a power law with exponent close to −0.8 was found for the concentrated system of LSB/1-butanol/water and 1% in weight of OG. On the contrary, the decrease in the viscosity by increasing the shear rate for the diluted system is less pronounced with lower exponent values. The rheological data agrees with the presence of vesicles. A special case is the system with benzyl alcohol. The apparent viscosity does not follow the same power law than for alkanols.

Constraints On the Large-Scale Porosity and Permeability Structure of Young Oceanic Crust From Velocity and Resistivity Data

SUMMARY Geophysical measurements of a single physical property provide weak constraints on the large-scale porosity structure of the sea-floor. This limitation arises from fundamental principles which may be overcome by examing two independent pieces of information. As an example, electrical resistivity values and seismic compressional velocities from the East Pacific Rise at 13N are simultaneously compared to various combinations of empirical expressions. The best agreement between theory and the data sets is found using either the connected Hashin-Shtrikman bound or, equivalently, Archie's law with a low value of exponent to describe the resistivities, and Wyllie's time-average equation for the seismic velocities. The combination implicitly requires a connected fluid distribution and, hence, a highly permeable crust throughout the uppermost 1 km of sea-floor. Porosities in the surface regions remain poorly constrained. Assuming a fluid temperature below 15 C predicts porosities of at least 20 per cent in the uppermost 50 m, decreasing to less than 1 per cent at depths around 1 km. Permeabilities of around 5 X lo-'' m2 are inferred for the surface regions decreasing to 3 X lo-'' m2 at depth. The method described should prove useful in constraining the structure in older sea-floor as more resistivity profiles are gathered along with seismic data.