Mercury Sensitivity Research Articles

The relevance and effect of amalgam replacement in subjects with oral lichenoid reactions

In this study we examined the prevalence of mercury hypersensitivity in patients with oral lichenoid reactions (OLR) and the effect of amalgam replacement in subjects with amalgams adjacent to OLR irrespective of their mercury sensitivity status. One hundred and ninety-seven patients with oral problems were examined: 109 with OLR, 22 with oral and generalized lichen planus, and 66 with other oral diagnoses, including aphthous ulcers and orofacial granulomatosis. Nineteen per cent of patients with OLR reacted to mercury on patch testing, significantly more than in those with generalized lichen planus (0%) and in those with other oral diagnoses (3%). Twenty-two patients with OLR and adjacent amalgams had amalgam replacement and, in 16 of 17 mercury-positive subjects and three of four mercury-negative subjects, the OLR resolved after amalgam removal. In conclusion, we found a significantly increased prevalence of mercury hypersensitivity in patients with localized OLR in comparison to subjects with other oral problems. Amalgam replacement resulted in resolution of OLR in the majority of patients with amalgams adjacent to OLR irrespective of their mercury sensitivity status.

Amorphous Hydrogenated Silicon Nitride Deposited by Mercury Photosensitization Chemical Vapour Deposition for Optoelectronic Applications

In this work we focus on the properties of amorphous hydrogenated silicon nitride (a-SiN:H) films deposited by mercury sensitization Photo-Chemical Vapour Deposition (Photo-CVD) utilizing SiH 4 and NH 3 and their suitability for the realization of III-V semiconductor optoelectronic devices (dielectric insulation, protection of reverse junctions, process mask, selective regrowth, antireflection coating). Using proper deposition conditions we have obtained a-SiN:H films with breakdown field of 8.9 MV/cm, good spatial uniformity of the dielectric properties, refractive index of 1.85 at 1535 nm, quasi-stoichiometric composition (Si/N=0.8), energy gap of 4.22 eV and density of 2.51 g/cm 3 , absence of pores and bubbles. We can reproduce film thickness, refractive index and energy gap within ±3%, ±0.005 and 0.05 eV respectively. SiN/InP structures similar to the actual optoelectronic devices have been employed in order to test mechanical adhesion and thichness of the a-SiN:H film grown on vertical facets. A-SiN:H films deposited in the optimized conditions have been successfully used in the previously mentioned applications.

The perfluoro-1,3,5-hexatrienes

trans-Perfluoro-1,3,5-hexatriene was obtained by catalytic isomerization of the cis isomer, and their configurations were confirmed by a photochemical method. Equilibration of these isomers with iodine and light at 13 o C revealed that the cis isomer is slightly more stable than the trans (K c→t =0.83). The trienes undergo reactions under the influence of heat and light which contrast with those of their hydrocarbon counterparts. Cis triene cyclizes reversibly to perfluoro-3-vinylcyclobutene at 160 o C (K eq =12.2), and at higher temperatures perfluoro-1,3-cyclohexadiene is formed irreversibly. Cyclization of trans triene to the vinylcyclobutene is much slower than that of the cis isomer, as required by the finding that thermal ring opening of the vinylcyclobutene gives cis triene cleanly. Ultraviolet irradiation of the trienes with and without mercury sensitization yields the same two cyclization products, but the cyclohexadiene undergoes a further rapid photocyclization to give perfluorobicyclo[2.2.0]hex-2-ene, as reported recently by Dedek's group. Mercury photosensitization of the vinylcyclobutene proceeds smoothly to yield this same bicyclic olefin

Oral lichenoid lesions and mercury sensitivity

Oral lichenoid lesions and mercury sensitivity

Enhancement of sensitivity of mercury fulminate upon irradiation

We have studied the change in the flash point and impact sensitivity of mercury fulminate upon irradiation with γ-rays from60Co and electron pulses.

Direct Nebulization of Sample Solution Containing Reductant for the Determination of Mercury by Inductively Coupled Plasma-Atomic Emission Spectrometry

Abstract In order to enhance the sensitivity of mercury, the most effective reductant, tin(II) chloride was added to a mercury solution, and the mixture was immediately introduced into the plasma through a conventional pneumatic nebulizer. The attainable detection limit for mercury was inproved from 79 ng ml−1 in the untreated solutions to 1.3 ng ml−1 when tin(II) chloride was added. The present method was successfully applied to the determination of trace concentrations of mercury in several samples of waste water.

A combination of rapid thermal processing and photochemical deposition for the growth of SiO2 suitable for InP device applications

A combination of ultraviolet and infrared lamps is used to obtain the growth of SiO2 on InP substrates at low temperature under rapid thermal processing conditions. Thorough infrared spectroscopy characterization of the dielectric layers shows that the ultraviolet-assisted growth process without mercury sensitization leads to good quality silica interspersed with oxygen-deficient inclusions. Rapid annealing improves them so as to be suitable for InP-based field-effect devices, with interface trap density around 5×1011 cm−2. A study of the interface trap density made with this technique shows the relevance of fast thermal processing, even at low growth temperatures, for the improvement of these devices.

Oral lichenoid reactions related to mercury sensitivity

Lichen planus is a common disorder of unknown aetiology. It has been proposed that in some cases it represents a form of allergic reaction to the metals contained in dental amalgam, particularly mercury. Twenty-nine consecutive dentate patients who had lichen planus of the oral mucosa were patch-tested to the range of metals contained in dental amalgam. Ten out of 29 (34%) showed an allergic reaction to mercury and all of these patients had amalgams greater than 5 years old. The amalgams were poorly contoured and had corroded, resulting in continued release of mercury ions. Six patients had their amalgams replaced with composite or glass ionomer materials resulting in resolution of ulcerated lesions. In a follow-up of 3–24 months, one patient had a recurrence of ulcerated areas and another, despite resolution of the oral lesions had persistent dicomfort.

Photochemical vapor deposition of silicon nitride films

A low temperature photochemical vapor deposition method utilizing mercury sensitization was used to deposit thin silicon nitride films. The chief advantages of the photochemical process are the low deposition temperatures, conformal coverage, reduction of electromagnetic radiation and charged species, and ability to tailor stoichiometry for specific applications. The effects of process variables upon the optical characteristics of nitride films were studied in this investigation. These properties were found to be variable over a wide range. Refractive index was strongly dependent upon the deposition temperature and ammonia/silane ratio, with higher temperatures and lower gas ratios yielding denser films, but at reduced deposition rates. The etch rate of these films was strongly influenced by the annealing temperature, with lower rates resulting at higher temperatures, consistent with increased densification and decreased pinhole densities. Electrical properties of typical films, including dielectric constant, breakdown strength, and mobile ion concentration were also determined.

Novel retinoid-binding proteins from filarial parasites.

The present study deals with the discovery and partial characterization of specific binding proteins for retinol and retinoic acid from filarial parasites (worms of the superfamily Filarioidea), including those from two species of Onchocerca. These binding proteins, which are distinct in their physicochemical properties and in the mode of ligand interactions from the host-tissue retinoid-binding proteins, may be involved in the mediation of the putative biological roles of retinoids in the control of parasitic growth, differentiation and reproduction. Parasite retinol-binding protein and retinoic acid-binding protein exhibited specificity for binding retinol and retinoic acid respectively. Both the binding proteins showed an s20,w value of 2.0 S. On gel filtration, both proteins were retarded to a position corresponding to the same molecular size (19.0 kDa). On preparative columns, the parasite binding proteins exhibited isoelectric points at pH 5.7 and 5.75. Unlike the retinoid-binding proteins of mammalian and avian origin, the parasite retinoid-binding proteins showed a lack of mercurial sensitivity in ligand binding. The comparative amounts of retinoic acid-binding protein in five parasites, Onchocerca volvulus, Onchocerca gibsoni, Dipetalonema viteae, Brugia pahangi and Dirofilaria immitis, were between 2.7 and 3.1 pmol of retinoic acid bound/mg of extractable protein. However, the levels of parasite retinol-binding protein were between 4.8 and 5.8 pmol/mg, which is considerably higher than the corresponding levels of cellular retinol-binding protein of mammalian and avian origin. Both retinol- and retinoic acid-binding-protein levels in O. volvulus-infected human nodules and O. gibsoni-infected bovine nodules were similar to their levels in mammalian tissues. Also, these nodular binding proteins, like the host-binding proteins, exhibited mercurial sensitivity to ligand interactions.

A Study of the Inter-elemental Effect in the Carbon-furnace Atomic-absorption Spectrometry of Selenium and Mercury in Biological Samples by the Palladium-addition Method

Abstract In the electrically-heated carbon-furnace atomic-absorption spectrometry of selenium and mercury, interelemental interference is present between the two elements. Mercury has no effect on selenium sensitivity in a simple inorganic selenium solution. When, however, the solution contains organic materials such as 0.5% albumin, the selenium sensitivity is decreased. The presence of mercury in addition to the organic material further decreases the sensitivity to about a half of that of a solution containing only selenium and albumin. The addition of 0.94 mmol dm−3 palladium ion completely removes the negative interferences due to organic materials and mercury. On the other hand, in mercury determination the presence of organic materials also decreases the mercury sensitivity. The addition of palladium, in contrast to selenium determination, enhances the mercury sensitivity about 50 times, independent of whether or not the solution contains organic materials.

Composite Resins

The interest in posterior composite resins has grown rapidly during the last several years. Much of the interest has been initiated by a demand for esthetic dentistry. Some has developed as a result of a concern by some for mercury sensitivity. Despite their growing popularity, a number of major problems persist. Some of these deal with the restorative material, whereas others relate to the clinical techniques associated with their use. Before the clinician considers the use of composite resins in posterior teeth, he or she should be familiar with conditions that strongly influence clinical behavior.

Saccharomyces cerevisiae strains sensitive to inorganic mercury. I. Effect of tyrosine.

From a cross of two strains of Saccharomyces cerevisiae, both of which had the same (wild type or normal) level of resistance to inorganic mercury, segregants having three distinguishable resistance levels, normal, sensitive and semi-sensitive, were obtained. Genetic analyses of the parents and the progeny indicated that the levels of inorganic mercury sensitivity were determined by three distinct loci, HGS1, HGS2 and MSM1. The recessive allele of the HGS1 locus, hgs1-1, and the codominant allele of the HGS2 locus, HGS2-1, were necessary for the sensitive phenotypes, and alleles in the MSM1 locus, MSM1-1 and msm1-2, were responsible for the different sensitivity levels. In short, the strains of genotypes hgs1-1 HGS2-1 msm1-2 and hgs1-1 HGS2-1 MSM1-1 were sensitive and semi-sensitive, respectively, while the strains of all other genotypes were normal. Although the hgs1-1 allele was identified as the aro7-1 mutation which confers deficiency of tyrosine and phenylalanine, mutations such as aro1B (deficiency of tyrosine, phenylalanine and tryptophan) and tyr1 (deficiency of tyrosine) had similar effects as aro7-1 on inorganic mercury sensitivity. From these results we conclude that the HGS2-1 allele causes inorganic mercury sensitivity when the cells are defective in the tyrosine biosynthesis. In fact, addition of tyrosine to the growth medium containing inorganic mercury resulted in increase of colony forming ability of the sensitive strains.

Development of a Continuous-Flow Hydride and Mercury Vapor Generation Accessory for Atomic Absorption Spectrophotometry

The design and performance characteristics of a continuous-flow vapor generation accessory for atomic absorption spectrophotometry are reported. When used with a conventional atomic absorption spectrophotometer, the accessory provides analytical sensitivity for mercury, arsenic, selenium, antimony, bismuth, tellurium, and tin equal or superior to that of a batch-type vapor generation device. Sample presentation, sample consumption, precision of measurement, and simplicity of operation are similar to those of flame atomic absorption with a pneumatic nebulizer. Details of the construction of the continuous-flow manifold, gas/liquid separator, and absorption cells are discussed, and the effects of reagent concentrations and carrier gas flow rates are shown. Characteristic concentrations and analytical curves for the above elements are also presented.

Sensitivity to antimicrobial agents of some mercury-sensitive and mercury-resistant strains of Gram-negative bacteria

The sensitivity and resistance of some Gram-negative mercury (Hg2+)-sensitive and-resistant strains to chemotherapeutic agents and to disinfectants and preservatives are described.Escherichia coli andPseudomonas aeruginosa strains harboring plasmid pUB 1351 [pUB 367:Tn 501] andE. coli bearing R100-1 were resistant to inorganic mercury and to various antibiotics, but were not more resistant to organic mercury and other preservatives and disinfectants than plasmidless strains.

Application of a Microwave-Induced Helium Plasma Detector at Atmospheric Pressure for Gas Chromatographic Capillary Columns

The analytical performance of a modified version of Beenakker's cavity (1) was evaluated as a microwave-induced plasma detector (MPD) for gas chromatographic capillary columns. The MPD compared favorably with the flame ionization detector (FID), with respect to gas chromatographic peak resolution and ease of operation. The FID performance was superior in detection limits and linear range for hydrocarbons. However, for organomercury compounds the MPD exhibited a greater sensitivity for mercury than that of the FID for carbon.

Reaction of hydrogen atoms with dimethyldisulfide

AbstractHydrogen atoms, generated by the mercury (3P1) sensitization of H2, were allowed to react with dimethyldisulfide in the temperature range of 25–155°C. The only retrievable product is methanethiol, formed in the primary metathetical reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm H} + {\rm CH}_3 {\rm SSCH}_3 {\rm CH}_3 {\rm SH} + {\rm CH}_3 {\rm S} $\end{document}. The intermediacy of thiyl radicals was clearly demonstrated in experiments carried out in the presence of ethylene where one of the major products detected was ethyl methyl sulfide, formed via CH3S + C2H5 → CH3SC2H5. The major fate of the CH3S radical is recombination and disproportionation, and the yield of methanethiol formed via disproportionation contributes less than 5% to the total thiol yield. The rate coefficient of step 1, from competition with the reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm H} + {\rm C}_{\rm 2} {\rm H}_{\rm 4} {\rm C}_{\rm 2} {\rm H}_5 $\end{document}, is k1 = (5.7 ± 1.2) × 1012 exp[(100 ± 100)/RT] cm3/mol sec.

Microwave detection of photolysis products: HCO from acetaldehyde using mercury sensitization

Four millimeter wave transitions of HCO have been re-measured using mercury sensitized photolysis of acetaldehyde. This is the first microwave spectra observation of a photochemically generated free radical. Measured loss rates of acetaldehyde indicate a photon efficiency of approximately 0.2%.

ChemInform Abstract: VAPOR‐PHASE PHOTOLYSIS OF CIS‐ AND TRANS‐4,5‐DIMETHYLCYCLOHEXENES

AbstractDie direkte Photolyse der Titelverbindungen führt unter Retro‐Diels‐Alder‐Spaltung zu Buten‐(2) und Butadien‐(1,3) unter Erhaltung der ursprünglichen Konfiguration, sowie zu 3,4‐Dimethyl‐1‐methylen‐cyclopentan.

Vapor-Phase Photolysis of cis- and trans-4,5-Dimethylcyclohexenes

Abstract Direct and sensitized photolyses of 4,5-dimethylcyclohexene vapor were investigated using a stereochemical approach at room temperature over the pressure range from 1 to 9 Torr. In the direct photolysis, decomposition of the retro-Diels-Alder type was the main course of the reaction, leading to the formation of 2-butene and 1,3-butadiene with the retention of the original configuration; 3,4-dimethyl-1-methylenecyclopentane was also formed as a minor product from a pressure-independent process. Mercury sensitization, on the other hand, produced cis- and trans-2-butenes, butadiene, 2,3-dimethyl-1-vinylcyclobutane, and cis-trans isomers of the substrate together with radical-induced products, i.e., hydrogen, 1,2-dimethylcyclohexane, and dimeric products. The intermediacy of a “hot,” “triplet” biradical was suggested from the pressure-dependence of the trans- to cis-2-butene ratio in the mercury sensitization. The differences in the results between the direct and sensitized photolyses are interpreted in terms of spin correlation effects.