XRMA analysis and X-ray diffraction analysis of dental enamel from human permanent teeth exposed to hydrogen peroxide of varying pH

Background: This in vitro investigation shows how 3.3% H2 O2 , at different pH-values affects the enamel. Material and Methods: A number of fifteen human premolars were used. The enamel of the coronal half in six of the teeth, were exposed by H2 O2 . Nine teeth were prepared to enamel powder. The enamel was exposed to 3.3% H2 O2 , at six different pH-values (pH range 4.5 - 7.0). Analyses of the topography of enamel performed by scanning electron microscope (SEM) and the chemical composition of enamel by X-ray microanalysis (XRMA). X-ray powder diffraction (XRD) analysed the crystallinity in enamel powder . Results: The exposure to H2 O2 at pH5.5 resulted in a decrease of O in the exposed enamel, and changes in C:P, Ca:C, Ca:P and Ca:O were observed. The H2 O2 2 did not affect the unit cell parameters, but the signal-to-noise level was increased for slightly acidic or neutral solutions. The unit cell parameters decreased in the acidic solutions. Conclusions: The exposure to H2 O2 at varying pH values affect the enamel with two different mechanisms. One effect is the oxidation of the organic or bioorganic matter in the hydroxyapatite matrix, due to the use of 3.3% H2 O2 . The other effect is due to the current pH of the H2 O2 , since the structure of the hydroxyapatite starts to erode when the pH<5.5

Kvinnligt och manligt – skilda estetiska gestaltningsprinciper

Some mediaevalists argue that the study of aesthetic aspects of mediaeval art is anachronistic, but mediaeval sculptors and painters clearly used a wide range of aesthetic means of expression. In hymns and liturgical texts Mary, the Mother God and epitome of all Christian virtues, is presented without defect or blemish. Although the evangelists have little or nothing to say about Mary’s looks, the mediaeval visionaries praised her celestial inner qualities and took it for granted that they corresponded to her outward appearance. Even on her death-bed Mary is depicted as an idealized young girl. The representations of later female saints were strongly influenced by the image of Mary.  – For both men and women humility was a valued Christian virtue, but particularly suited for the weaker sex. In hagiographies, men are sometimes represented as meek and humble, but in pictorial art they are often rendered as quite arrogant. Information on the male saints’ appearances is extremely rare but individualization soon gave their faces a kind of portrait character, a tendency that became even more obvious in the late Middle Ages. Whereas female saints frequently have an anonymously bland, impersonal appearance, men are often represented as individuals. The pictorial means by which these differences were attained cannot be described as other than “aesthetic”

Energy levels in resting and mitogen-stimulated human lymphocytes during treatment with FK506 or cyclosporin A in vitro

AbstractBy employing microcalorimetry to assess overall metabolic activity in combination with other assays for specific metabolic events, we have investigated the influence of cyclosporin A and FK506 on the metabolic status of resting and mitogen-stimulated human peripheral lymphocytes. Both cyclosporin A and FK506 significantly reduced heat output from resting lymphocytes. This reduction could not be correlated with effects on DNA synthesis, lactate production, ATP levels or mitochondrial uptake of Rhodamine 123. These two drugs also potently reduced the increase in heat output seen during mitogen stimulation of lymphocytes. Both cyclosporin A and FK506 also prevented the increase in DNA synthesis, lactate production and ATP levels seen in response to mitogen stimulation. The increase in mitochondrial uptake of Rhodamine 123 during blastoid transformation was significantly reduced only by cyclosporin A. We ascribe the major part of the effects of these compounds to inhibition of the glycolytic pathway in both resting and mitogen-stimulated lymphocytes. These results indicate that the immunosuppressants cyclosporin A and FK506 exert other effects on lymphocytes than their well-established inhibitory action on calcineurin.© 1997 Elsevier Science B.V. All rights reserved

Bioaccessibility, bioavailability and toxicity of commercially relevant iron- and chromium-based particles: in vitro studies with an inhalation perspective

<p>Abstract</p> <p>Background</p> <p>Production of ferrochromium alloys (FeCr), master alloys for stainless steel manufacture, involves casting and crushing processes where particles inevitably become airborne and potentially inhaled. The aim of this study was to assess potential health hazards induced by inhalation of different well-characterized iron- and chromium-based particles, i.e. ferrochromium (FeCr), ferrosiliconchromium (FeSiCr), stainless steel (316L), iron (Fe), chromium (Cr), and chromium(III)oxide (Cr₂O₃), in different size fractions using in vitro methods. This was done by assessing the extent and speciation of released metals in synthetic biological medium and by analyzing particle reactivity and toxicity towards cultured human lung cells (A549).</p> <p>Results</p> <p>The amount of released metals normalized to the particle surface area increased with decreasing particle size for all alloy particles, whereas the opposite situation was valid for particles of the pure metals. These effects were evident in artificial lysosomal fluid (ALF) of pH 4.5 containing complexing agents, but not in neutral or weakly alkaline biological media. Chromium, iron and nickel were released to very low extent from all alloy particles, and from particles of Cr due to the presence of a Cr(III)-rich protective surface oxide. Released elements were neither proportional to the bulk nor to the surface composition after the investigated 168 hours of exposure. Due to a surface oxide with less protective properties, significantly more iron was released from pure iron particles compared with the alloys. Cr was predominantly released as Cr(III) from all particles investigated and was strongly complexed by organic species of ALF. Cr₂O₃particles showed hemolytic activity, but none of the alloy particles did. Fine-sized particles of stainless steel caused however DNA damage, measured with the comet assay after 4 h exposure. None of the particles revealed any significant cytotoxicity in terms of cell death after 24 h exposure.</p> <p>Conclusion</p> <p>It is evident that particle and alloy characteristics such as particle size and surface composition are important aspects to consider when assessing particle toxicity and metal release from alloy particles compared to pure metal particles. Generated results clearly elucidate that neither the low released concentrations of metals primarily as a result of protective and poorly soluble surface oxides, nor non-bioavailable chromium complexes, nor the particles themselves of occupational relevance induced significant acute toxic response, with exception of DNA damage from stainless steel.</p

Влияние национального менталитета на инновационную политику Республики Беларусь

Материалы VII междунар. науч. конф., 26-27 мая 2011 г

A Pediatric Bone Mass Scan Has Poor Ability to Predict Adult Bone Mass: A 28-Year Prospective Study in 214 Children.

As the correlation of bone mass from childhood to adulthood is unclear, we conducted a long-term prospective observational study to determine if a pediatric bone mass scan could predict adult bone mass. We measured cortical bone mineral content (BMC [g]), bone mineral density (BMD [g/cm(2)]), and bone width (cm) in the distal forearm by single photon absorptiometry in 120 boys and 94 girls with a mean age of 10 years (range 3-17) and mean 28 years (range 25-29) later. We calculated individual and age-specific bone mass Z scores, using the control cohort included at baseline as reference, and evaluated correlations between the two measurements with Pearson's correlation coefficient. Individual Z scores were also stratified in quartiles to register movements between quartiles from growth to adulthood. BMD Z scores in childhood and adulthood correlated in both boys (r = 0.35, p < 0.0001) and girls (r = 0.50, p < 0.0001) and in both children ≥10 years at baseline (boys r = 0.43 and girls r = 0.58, both p < 0.0001) and children <10 years at baseline (boys r = 0.26 and girls r = 0.40, both p < 0.05). Of the children in the lowest quartile of BMD, 58 % had left the lowest quartile in adulthood. A pediatric bone scan with a value in the lowest quartile had a sensitivity of 48 % (95 % confidence interval [CI] 27-69 %) and a specificity of 76 % (95 % CI 66-84 %) to identify individuals who would remain in the lowest quartile also in adulthood. Childhood forearm BMD explained 12 % of the variance in adult BMD in men and 25 % in women. A pediatric distal forearm BMD scan has poor ability to predict adult bone mass

Comparison and Evaluation of Multiple Users' Usage of the Exposure and Risk Tool: Stoffenmanager 5.1.

Stoffenmanager is an exposure and risk assessment tool that has a control banding part, with risk bands as outcome and a quantitative exposure assessment part, with the 90th percentile of the predicted exposure as a default outcome. The main aim of the study was to investigate whether multiple users of Stoffenmanager came to the same result when modelling the same scenarios. Other aims were to investigate the differences between outcomes of the control banding part with the measured risk quota and to evaluate the conservatism of the tool by testing whether the 90th percentiles are above the measured median exposures. We investigated airborne exposures at companies in four different types of industry: wood, printing, metal foundry, and spray painting. Three scenarios were modelled and measured, when possible, at each company. When modelled, 13 users visited each company on the same occasion creating individual assessments. Consensus assessments were also modelled for each scenario by six occupational hygienists. The multiple users' outcomes were often spread over two risk bands in the control banding part, and the differences in the quantitative exposure outcomes for the highest and lowest assessments per scenario varied between a factor 2 and 100. Four parameters were difficult for the users to assess and had a large impact on the outcome: type of task, breathing zone, personal protection, and control measures. Only two scenarios had a higher measured risk quota than predicted by the control banding part, also two scenarios had slightly higher measured median exposure value than modelled consensus in the quantitative exposure assessment part. Hence, the variability between users was large but the model performed well

Analysis of the contributions to the performance of a functional product design using simulation

Functional products (FP) consist of combined hardware, software and support services that are sold to the customer under performance-based contracts that guarantee a specified level of functional availability. The supplier is responsible for the development, manufacture, support and upgrade of a FP during the contract period. In comparison to a traditional hardware sale only contract, an FP transfers risk from uncertain availability and support costs from the customer to the supplier. This is a major advantage for the customer but means that the supplier must understand and optimise the availability and support costs of a FP design. During product development, simulation can be used to analyse potential FP designs, predict how they will perform and identify possible areas for improvement – providing vital qualitative and quantitative decision support. In this paper, a methodology for analysing a FP design to predict how it will perform and determine the contribution of individual elements of the FP to its overall performance is described. This methodology is then applied to analyse an example of a FP

Polarization Effects in Superdeformed Nuclei

A detailed theoretical investigation of polarization effects in superdeformed nuclei is performed. In the pure harmonic oscillator potential it is shown that when one particle (or hole) with the mass single-particle quadrupole moment q_{nu} is added to a superdeformed core, the change of the electric quadrupole moment can be parameterized as q_{eff}=e(bq_{nu}+a), and analytical expressions are derived for the two parameters, $a$ and $b$. Simple numerical expressions for q_{eff}(q_\nu}) are obtained in the more realistic modified oscillator model. It is also shown that quadrupole moments of nuclei with up to 10 particles removed from the superdeformed core of 152Dy can be well described by simply subtracting effective quadrupole moments of the active single-particle states from the quadrupole moment of the core. Tools are given for estimating the quadrupole moment for possible configurations in the superdeformed A 150-region.Comment: 28 pages including 9 figure

Modification and cross-linking parameters in hyaluronic acid hydrogels—Definitions and analytical methods

AbstractDefinitions and methods for the quantification of degree of modification and cross-linking in cross-linked hyaluronic acid (HA) hydrogels are outlined. A novel method is presented in which the HA hydrogel is degraded by the enzyme chondroitinase AC and the digest product analyzed by size exclusion chromatography combined with electrospray ionization mass spectrometry (SEC–ESI-MS). This method allows for the determination of effective cross-linker ratio (CrR) which together with the degree of modification (MoD), determined by, e.g. 1H NMR spectroscopy, enables the calculation of the degree of substitution (DS) and degree of cross-linking (CrD).The method, could be applicable to the major cross-linked HA hydrogels currently on the market, and is exemplified here by application to two HA hydrogels. The definitions and methods presented are important contributions in attempts to find relationships between MoD, DS and CrD to mechanical properties as well as to biocompatibility of HA hydrogels