Dentists' variability in restorative decisions, microscopic and radiographic caries depth

Restorative and dental caries depth decisions were recorded for 5168 un restored approximal tooth surfaces by 17 dentists who worked in the school dental clinics of the North York (Ontario) Public Health Department. Each dentist examined 15 pairs of experimental bitewing radiographs for which true caries depth had previously been determined by microscopy of the sectioned teeth following production of the radiographs. The dentists independently recorded their restorative decisions and radiographic caries depth perceptions. The relationship between the variation in the dentists' restorative decisions and their perceptions of caries depth based on a re-reading of the bitewings on the one hand, and true caries depth on the other was also examined. The percentages of total variability in each dentist's restorative decisions attributable to radiographic and to microscopic caries depth were estimated using regression analyses. Large variations were found among the 17 dentists' distributions of overall restorative and depth decisions. The relationship between microscopic caries depth and the dentists' restorative decisions was, understandably, less strong than that of the dentists radiographic perceptions of caries depth and restorative decisions. Relative to true caries depth, high numbers of false positive and false negative restorative decisions were made. Overall, 50% of the variability in the dentists' restorative decisions was explained by the perceptions of radiographic caries depth; however, among individual dentists, the range was from 29% for one dentist to 69% for another. A much lower percentage of the overall restorative variation was explained by microscopic depth, 18%. Like the finding of the only two previous European studies that quantified the role of radiographs on clinical decisions, this study demonstrated that dentists' perceptions of dental caries depth using bitewing radiographs play a major but variable role in their restorative decisions for approximal tooth surfaces.     

High-gain plasma Cerenkov maser

The linearized fluid and Maxwell's equations are used to calculate the dispersion relation for the transverse magnetic modes of a partially filled, plasma-lined, cylindrical waveguide interacting with a relativistic electron beam. Both the plasma liner and the electron beam are assumed to be cold, and the system is immersed in an infinite axial magnetic guide field. The dispersion relation is then used to calculate the growth rate for the instability between the slow-wave modes (Trivelpiece-Gould modes) of the plasma guide and the slow-space charge mode of the electron beam. The calculation is done in the high-gain, strong coupling limit     

Load‐Deflection Behavior of Space‐Based Inflatable Fabric Beams

The use of inflatable structures has often been proposed for aerospace applications. The advantages of such structures include low launch weight and easy assembly. To consider using inflated fabric beams in aerospace applications, an accurate and efficient method of structural analysis must be developed. This paper develops a method of analysis for inflated fabric beams that is analogous to the shear‐moment method. The bending model is developed from basic assumptions about the state of stress in the fabric of the inflated beam. The resulting model shows that the bending behavior of inflatable fabric beams is identical to conventional solid elastic beams as long as the beam fabric remains unwrinkled. Experimental data were obtained and verify the static bending model for beams with length/diameter ratios greater than 10.     

Lipids of retina: I. Analysis of gangliosides in beef retina by thin layer chromatography

Lipids were extracted from beef retina by chloroform-methanol (2∶1); the gangliosides were removed from the total lipid extract by partitioning into water and chromatographing on thin layer plates coated with silica gel. The analytical methods are described for estimating ganglioside components, i.e., N-acetyl neuraminic acid, hexoses, hexosamine, sphingosine and fatty acids, in the presence of silica gel. Major gangliosides present in beef retina have been tentatively identified as follows: a ganglioside containing two N-acetyl neuraminyl groups but no hexosamine; two gangliosides containing two N-acetyl neuraminyl groups and one hexosamine; and a ganglioside with three N-acetyl neuraminyl moieties and one hexosamine.     

Factors affecting incorporation of precursors into body constituents: A review of common sense considerations with glycolipids as examples

The dynamics of cellular growth are of prime importance to the biochemist. The dynamic state of lipids can be studied by employing radioactive substrates or stable isotope-labeled substrates. This paper illustrates major factors which may effect the incorporation of precursor substances into body constitutents. These factors are: (a) age and species; (b) molar size of the body’s pool of precursor; (c) metabolic activity of the lipid being synthesized; (d) metabolic pathways; (e) route of administration of the precursor; (f) the nature of the precursor, i. e., molecular size, ionic or nonionic, water soluble vs. lipid solubility, and micelle formation; and (g) the influence of hormones and drugs. The synthesis and turnover of cerebrosides and gangliosides in the rat are used to illustrate these seven factors.     

Experimental and numerical iInvestigations of effects of silica colloids on transport of strontium in saturated sand columns

Transport experiments with strontium were conducted using saturated sand columns in the presence and absence of silica colloids, and numerical modeling was performed with modeling results compared to experimental data. The experiments were aimed at testing the hypothesis that under certain chemical conditions colloids act as movement-retarding agents and yield a larger effective retardation factor for the migrating contaminant. Four individual experiments were conducted to identify conditions where the mobility of silica colloids is increased or decreased, and a similar set was conducted for strontium transport in the absence of colloids. Mobility of colloids was found to increase with decreasing ionic strength and increasing pH, with the ionic strength having the more significant impact. The reverse effect was obtained for strontium. Based on these results, two additional experiments were conducted where both colloids and strontium were injected at the column inlet. Results showed that under certain conditions of ionic strength and pH (I = 3.0 x 10(-2) M and pH = 4-5.4) colloids retarded the movement of strontium. The retardation effect was obtained in two experiments under slightly modified conditions, which confirms the role of colloids as retarding agents. Afinite difference numerical model was used to (a) simulate mobile breakthrough curves and compare to experimental data and (b) estimate the model parameters describing cotransport of strontium and colloids. The model accurately predicted arrival time and the overall shape of the breakthrough curves.     

Electronic structure of the Zn(O,S)/Cu(In,Ga)Se2 thin‐film solar cell interface

The electronic band alignment of the Zn(O,S)/Cu(In,Ga)Se₂ interface in high‐efficiency thin‐film solar cells was derived using X‐ray photoelectron spectroscopy, ultra‐violet photoelectron spectroscopy, and inverse photoemission spectroscopy. Similar to the CdS/Cu(In,Ga)Se₂ system, we find an essentially flat (small‐spike) conduction band alignment (here: a conduction band offset of (0.09 ± 0.20) eV), allowing for largely unimpeded electron transfer and forming a likely basis for the success of high‐efficiency Zn(O,S)‐based chalcopyrite devices. Furthermore, we find evidence for multiple bonding environments of Zn and O in the Zn(O,S) film, including ZnO, ZnS, Zn(OH)₂, and possibly ZnSe. Copyright © 2016 John Wiley & Sons, Ltd.     

Heat capacity of3He/4He mixtures

We measured the specific heat capacity of three dilute mixtures (2.6, 1.07, and 0.44%) of³He in⁴He and of pure⁴He. The⁴He contribution to the specific heat of the mixture is subtracted, leaving only the³He part. This is fitted to a theoretical expression over the whole temperature range from 10 to 700 mK. Assuming a dispersion relation of the form =² k ²(1+k ²)/2m*, the fits yield the value of and the effective mass m* of each mixture. The average value of is –0.076±0.01 A² and the effective mass in the limit of zero concentration is (2.23±0.02)m ₃. These are compared to values deduced from other measurements.