Effect of calcium hydroxide mixed with preservatives on physicochemical characteristics and sensory shelf-life of corn tortilla.

BACKGROUND: The objective of the study was to evaluate the physicochemical characteristics and shelf-life of corn tortilla stored at room temperature (25 °C) using aw modifiers (propylene glycol and glycerol) and pH modifiers (fumaric acid and sodium benzoate) as preservatives combined with calcium hydroxide. Detection thresholds were used to determine the maximum preservative concentration and calcium hydroxide. Physicochemical characterization and sensory evaluation were used to determine the stability and sensory shelf-life of tortillas. RESULTS: Control, calcium hydroxide, calcium hydroxide + fumaric acid, calcium hydroxide + glycerol, calcium hydroxide + propylene glycol, and calcium hydroxide + sodium benzoate treatments had rounded half-lives of 1, 2, 1, 2, 2, and 2 days respectively. Glycerol combined with calcium hydroxide resulted in tortillas with lower pH variations over time. Mold presence was the critical attribute causing tortilla rejection. CONCLUSION: The use of aw modifiers had a better effect in preserving corn tortilla, as the concentration of pH modifiers at detection threshold levels was not able to reach an optimum performance when combined with calcium hydroxide. © 2021 Society of Chemical Industry.

Characterization and analyses of acid-extractable and leached trace elements in dental cements.

AIMS: Determination of the elemental constitution and investigation of the total and leachable arsenic, chromium and lead in Portland cement, pure tricalcium silicate, Biodentine, Bioaggregate and mineral trioxide aggregate (MTA) Angelus. METHODOLOGY: The chemical composition of Portland cement, MTA Angelus, tricalcium silicate cement, Biodentine and Bioaggregate was determined using X-ray fluorescence (XRF). Measurements of arsenic, lead and chromium were taken with inductively coupled plasma-mass spectrometry (ICP-MS), following acid digestion on the hydrated material and on leachates of cements soaked in Hank's balanced salt solution (HBSS). RESULTS: All the cements investigated had a similar oxide composition with the main oxide being calcium and silicon oxide. Both the Portland cement and MTA Angelus had an additional aluminium oxide. The dental cements included a radiopacifying material. All the materials tested had higher acid-extractable arsenic content than the level set by ISO 9917-1 (2007) and an acceptable level of lead. Regardless these high levels of trace elements present in the materials, the leaching in HBSS was minimal for all the dental material tested in contrast to the high levels displayed by Portland cement. CONCLUSIONS: Dental materials based on tricalcium silicate cement and MTA Angelus release minimal quantities of trace elements when in contact with simulated body fluids. The results of acid extraction could be affected by nonspecific matrix effects by the cement.

A blue arsenomolybdic acid-crystal violet ion-associate pair paving the way for the field detection of arsenic in groundwater.

A simple visual colorimetric method based on arsenomolybdic acid-crystal violet ion-associate pair formation is described for the detection of As in groundwater at about 10, 25 and 50 µg L-1 levels. The pair exhibits light green coloration at ≤5 µg L-1 and blue colorations of distinctly different intensities at about 10, 25 and 50 µg L-1 concentrations of arsenic. High sensitivity is achieved by the preconcentration of As that entails simultaneous sorption of both As(III) and As(V) from groundwater on covellite (CuS) and, later, their elution as As(V), which subsequently participates in the formation of arsenomolybdic acid. The interference in the color development from PO43-ions that are as efficiently sorbed on CuS and eluted as the oxyanions of As is eliminated by their selective removal by Ce4+ ions under basic (pH ∼ 8.5) conditions. The removal is caused by the formation of cerium phosphate and its co-precipitation with calcium hydroxide. SiO42- ions do not interfere in the process as they are not sorbed by CuS. Groundwater containing ≤0.5 mg L-1 P and ≥200 mg L-1 total dissolved solid can be conveniently analysed by the method. The direct sensing of As(III) as well as As(V), the use of benign and easily available chemicals, the absence of any hazardous by-product, undiminished applicability in sunlight, the testing procedure lasting only for about 30 min, and rapidity are the major advantages of the method. Thus, the method is potentially well-suited for the on-site testing of groundwater potability under different regulations.

The effect of calcium hydroxide on the steroid component of Ledermix and Odontopaste.

AIM: To investigate the chemical interaction of calcium hydroxide with the corticosteroid triamcinolone acetonide in Ledermix Paste and in Odontopaste, a new steroid/antibiotic paste. METHODOLOGY: Validated methods were developed to analyse the interaction of calcium hydroxide in two forms, Pulpdent Paste and calcium hydroxide powder, with triamcinolone acetonide within Odontopaste and Ledermix Paste. High-performance liquid chromatography (HPLC) was used to analyse the mixed samples of the pastes and calcium hydroxide. The concentration of triamcinolone acetonide within the pastes was determined over 0, 2, 6, 24 and 72-h time-points. All tests with the HPLC involved the testing of the standard with triplicate injections alongside the samples. All samples were tested in duplicate with each injected twice; therefore, four tests were performed for each investigation. Linearity, precision and specificity of the testing procedures and apparatus were validated. Descriptive statistics are provided. RESULTS: In both pastes, there was a marked rapid destruction of the triamcinolone acetonide steroid upon mixing with calcium hydroxide. Odontopaste suffered a lower rate of destruction of the triamcinolone acetonide component than Ledermix Paste, but both pastes showed very similar degrees of steroid destruction after 72 h. When using calcium hydroxide powder with Ledermix Paste, the triamcinolone was destroyed entirely and immediately. CONCLUSION: The addition of calcium hydroxide to Odontopaste or Ledermix Paste results in the rapid destruction of the steroid.

[Effect of calcium hydroxide concentration and cooking time of corn grain (Zea mays L.) nixtamalized, over physicochemical and rheological nixtamal characteristics]. / Efecto de la concentración de hidr6xido de calcio y tiempo de cocción del grano de maíz (Zea mays L.) nixtamalizado, sobre las caracteristicas fisicoquímicas y reológicas del nixtamal.

The effect of calcium hydroxide (Ca(OH)2) concentration and cooking time on physicochemical and pasting properties of maize, during traditional nixtamalization was evaluated. It was observed that the higher the Ca(OH)2 concentration and cooking time the higher the gelatinization temperature. Grain samples treated with 2 g/100 g of Ca(OH)2 and 60 min of cooking time presented higher calcium absorption (0.152 g/100 g) showing a significant increment (approximately 500 g/100 g). Results of X-ray diffraction showed that all the samples had X-ray diffraction pattern of starch type A, showing differences in the intensity of the diffraction as indicated by the percentage of cristallinity. The apparent viscosity of the nixtamal considerably decreased when the processes conditions were higher. Water retention capacity increased with temperature.

Characterization of hydration products of mineral trioxide aggregate.

OBJECTIVE: To characterize the hydration products of white mineral trioxide aggregate (MTA). METHODOLOGY: Mineral trioxide aggregate, white Portland cement and bismuth oxide were evaluated using X-ray diffraction (XRD) analysis and Rietveld XRD. The cements were tested un-hydrated and after hydration and curing for 30 days at 37 degrees C. Analysis of hydrated cement leachate was performed weekly for five consecutive weeks from mixing using inductively coupled plasma atomic emission spectroscopy after which the cements were viewed under the scanning electron microscope to evaluate the cement microstructure. Quantitative energy dispersive analysis with X-ray was performed and atomic ratios were plotted. RESULTS: Both Portland cement and MTA produced calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) on hydration. The tricalcium aluminate levels were low for MTA which resulted in reduced production of ettringite and monosulphate. On hydration the bismuth level in the hydrated MTA decreased; bismuth oxide replaced the silica in the C-S-H and was leached out once the C-S-H decomposed with time. Both MTA and Portland cement released a high amount of calcium ions which decreased in amount over the 5-week period. CONCLUSIONS: The hydration mechanism of MTA is different to that of Portland cement. In MTA the bismuth oxide is bound to the C-S-H and is leached out from the cement with time as the C-S-H decomposes. MTA produces a high proportion of calcium ions from CH a by-product of hydration and also by decomposition of C-S-H. The release of calcium ions reduces with time.

Influence of glass-ionomer cement on the interface and setting reaction of mineral trioxide aggregate when used as a furcal repair material using laser Raman spectroscopic analysis.

The prolonged setting time of mineral trioxide aggregate (MTA) is the main disadvantage of this material. This study analyzes the influence of glass-ionomer cement on the setting of MTA using laser Raman spectroscopy (LRS). Forty hollow glass molds were taken in which MTA was placed. In Group I specimens, MTA was layered with glass-ionomer cement after 45 minutes. Similar procedures were done for Groups II and III at 4 hours and 3 days, respectively. No glass ionomer was added in Group IV, which were then considered as control samples. Each sample was scanned at various time intervals. At each time interval, the interface between MTA and glass-ionomer cement was also scanned (excluding Group IV). The spectral analysis proved that placement of glass-ionomer cement over MTA after 45 minutes did not affect its setting reaction and calcium salts may be formed in the interface of these two materials.

Sewage sludge stabilisation with calcium hydroxide: effect on physicochemical properties and molecular composition.

Raw primary sewage sludge (Wastewater Treatment Plant of Krotoszyn, SW Poland) and its mixtures with 3%d, 6%d, 9%d, 12%d and 24%d of calcium hydroxide were stabilised for 1 and 35 days. Changes of the sludge physicochemical properties and molecular composition, caused by alkaline agent in course of stabilisation process, are recognised. A basic physicochemical data on the sludge cake and filtrate after 1 and 35 days of stabilisation process are given. Soxhlet extracts from the sludge cakes stabilised for 35 days as well pyrolysis and pyrolysis in situ methylation (using tetramethylammonium hydroxide-TMAH) products of respective pre-extracted cake residues were analysed by gas chromatography-mass spectrometry (GC-MS). Increase of calcium hydroxide concentration in the sludge mixture causes enhanced ammonia release, preferential hydrolyses of fats and proteins from the sludge macromolecular network and transformation of free fatty acids contained in the sludge lipids, as well as these released hydrolytically, to their calcium salts. The sewage sludge stabilisation with calcium hydroxide has no effect on homological assemblage and content of unbound stanol and sterol compounds in the sludge lipids and these bound into macromolecular network. Biogenic n-alkanes and anthropogenic linear alkylbenzenes were detected as minor components in the lipids and pyrolytic products from the pre-extracted cake residue, respectively. The alkaline agent used for the sludge stabilisation accelerates equilibration of the process and reduces content of pathogenic microorganisms.

Remoción de hidróxido de calcio del canal radicular con irrigación manual, sónica y ultrasónica / Calcium hydroxide removal from the root canal by manual, sonic and ultrasonic irrigation

Introducción: Resulta fundamental la remoción por completo del hidróxido de calcio previo a la obturación del canal radicular que podría impedir la penetración de los selladores en los túbulos dentinarios. Objetivo: Determinar la efectividad de la eliminación de la medicación con hidróxido de calcio del canal radicular de dientes utilizando diferentes sistemas de irrigación. Métodos: Se irrigaron con hipoclorito de sodio 148 conductos radiculares rectos de dientes humanos. Se utilizó Ca(OH)2 mezclado con tinta negra para rellenar los canales radiculares y facilitar la visualización. Los dientes se dividieron en 5 grupos de acuerdo al protocolo de eliminación. En cada uno de los grupos, la extrusión apical se midió durante la etapa de irrigación por el método Huang X, después de la eliminación del Ca(OH)2, se seccionaron longitudinalmente y luego, en un portaobjetos, se observaron las muestras bajo un microscopio óptico. Finalmente, se analizó el contenido para cuantificar el grado de extrusión causado durante el procedimiento clínico. Se utilizó el test de ANOVA para el análisis estadístico Resultados: Se encontró diferencias significativas entre los grupos 1-2, 1-3, 1-4 y 1-5. El promedio de remanecía fue superior (66,4 por ciento). Los grupos 2 (41,6 por ciento) y 5 (34,8 por ciento) obtuvieron mayor eficacia en la remoción. ANOVA (α = 0,05) determina que no existieron diferencias significativas entre los 5 grupos. Conclusiones: Los dispositivos de activación ultrasónica mostraron una mayor eliminación de la medicación con hidróxido de calcio desde las paredes dentinarias a las técnicas manuales, sin embargo, demostró ser una terapia más invasiva debido a una mayor extrusión de detritus(AU)

Introduction: Root canal sealing should indispensably be preceded by complete calcium hydroxide removal, otherwise the latter might prevent the penetration of the sealers into the dentinal tubules. Objective: Determine the effectiveness of eliminating calcium hydroxide medication from the root canal of teeth using various irrigation systems. Methods: Preparation was conducted of 148 straight root canals of human teeth irrigating with sodium hypochlorite. The root canals were filled with Ca(OH)2 mixed with black ink to facilitate visualization. The teeth were divided into 5 groups in compliance with the removal protocol. Apical extrusion was measured in each group during the irrigation stage using the Huang X method. After Ca(OH)2 removal they were sectioned longitudinally and placed on a slide for observation of the samples under an optical microscope. Finally the content was analyzed to quantify the degree of extrusion obtained during the clinical procedure. The ANOVA test was used for statistical analysis. Results: Significant differences were found between the groups 1-2, 1-3, 1-4 and 1-5. Average remanence was above 66.4 percent. Groups 2 (41.6 percent) and 5 (34.8 percent) displayed higher removal efficacy. ANOVA (α = 0.05) did not determine any significant differences between the 5 groups. Conclusions: Ultrasonic activation obtained greater calcium hydroxide removal from the dentinal walls than manual techniques. However, it proved to be a more invasive therapy due to the greater detritus extrusion(AU)

Efeito antibiofilme e citotoxicidade do hidróxido de cálcio associado ao óleo essencial de Melaleuca alternifolia / Antibiofilm effect and cytotoxicity of calcium hydroxide associated with the Melaleuca alternifolia essential oil

Objetivo: Avaliar e comparar os efeitos antimicrobiano e antibiofilme, e a citotoxicidade promovida pela associação do hidróxido de cálcio ao óleo essencial de Melaleuca alternifolia (MA), em diferentes concentrações, e ao propilenoglicol (PG). Métodos: As seguintes medicações compuseram os grupos experimentais: G1) HC/MA 1%; G2) HC/MA 5%; G3) HC/MA 10%; G4) HC/MA 20%; e G5) HC/PG. Solução salina 0,85% e meio DMEM serviram como controle nos testes antimicrobianos e de citotoxidade em fibroblastos do ligamento periodontal humano (FbLP), respectivamente. A atividade antimicrobiana (n = 12) foi avaliada por meio do teste de difusão em ágar. O efeito antibiofilme (n = 12) imediato das medicações foi avaliado por meio do teste de viabilidade bacteriana em biofilmes de 72 horas de E. faecalis, formados sobre discos de dentina e tratados por sete dias com as medicações. Após a coleta microbiológica do biofilme remanescente, os discos de dentina foram imersos em meio estéril e armazenados por mais sete dias, para a análise do efeito antibiofilme residual das medicações, quando nova coleta microbiológica foi realizada. A atividade metabólica de FbLP foi avaliada por meio do ensaio colorimétrico MTS (n = 9). Os valores médios dos halos de inibição, em mm, das unidades formadoras de colônia, e o percentual de atividade metabólica celular foram analisados pelos testes Kruskal-Wallis e post hoc Dunn (α = 5%). Resultados:Todas as medicações experimentais apresentaram superior ação antimicrobiana e antibiofilme comparadas ao controle, solução salina (p < 0,05), e mantiveram viáveis os FbLP, semelhante ao controle DMEM (p > 0,05). Conclusão: A associação do óleo essencial de Melaleuca alternifolia, nas concentrações de 1%, 5%, 10% e 20%, ao hidróxido de cálcio promoveu excelente ação antimicrobiana, antibiofilme e biocompatibilidade com fibroblastos, de forma semelhante à associação com propilenoglicol.

Aim:To evaluate and compare the antimicrobial and antibiofilm effect, as well as the cytotoxicity of calcium hydroxide (CH) associated with the Melaleuca alternifolia (MA)essential oil, in different concentrations, and with propylene glycol. Methods: The following medications composed the experimental groups: G1) CH/MA 1%; G2) CH/MA 5%; G3) CH/MA 10%; G4) CH/MA 20%; and G5) CH/PG. Saline solution and culture medium DMEM were used as a control in antimicrobial and cytotoxicity tests in human periodontal ligament fibroblasts (PDLF), respectively. The antimicrobial activity (n = 12) was evaluated by the disk-diffusion agar method. The immediate antibiofilm effect (n = 12) of the medications was evaluated for bacterial viability in 72 hours-biofilms of E. faecalis, formed on the dentin disc surface and treated for seven days with medications. After microbiological sampling of the remaining biofilm, the dentin discs were immersed in sterile culture medium and stored for another seven days, for analysis of the residual antibiofilm effect of the medications, when a new microbiological sampling was performed. PDLF viability was evaluated by MTS colorimetric assay (n = 9). The mean values of the inhibition halos, in mm, the colony forming units, and the metabolic cell activity percentage were analyzed by means of Kruskal-Wallis and post hoc Dunn (α = 5%) tests. Results:All of the experimental medications presented higher antimicrobial and antibiofilm effects, when compared to the saline solution control (p < 0.05), and maintained the PDLF feasible, similar to the DMEM control (p > 0.05). Conclusions:The association of the Melaleuca alternifolia essential oil, at concentrations of 1%, 5%, 10%, and 20%, with calcium hydroxide promoted an excellent antimicrobial and antibiofilm activity, and biocompatibility with fibroblasts, similarly to the association with propylene glycol.

Efficacy of Needle, Ultrasonic, and Endoactivator Irrigation and Photon-Induced Photoacoustic Streaming in Removing Calcium Hydroxide from the Main Canal and Isthmus: An In Vitro Micro-Computed Tomography and Scanning Electron Microscopy Study.

OBJECTIVE: The aim of this in vitro study was to use high-resolution micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to compare the efficacy of four irrigation techniques [needle, ultrasonic, EndoActivator, and photon-induced photoacoustic streaming (PIPS)] in removing calcium hydroxide (Ca[OH]2) from the root canal and isthmus of maxillary premolars. METHODS: Twenty-four maxillary first premolars were selected based on the presence of isthmus regions on micro-CT scans. Root canals were instrumented with an F2 file using ProTaper rotary instruments and filled with Ca(OH)2 paste. Samples were stored at 37°C and 100% humidity for 1 week and randomly divided into four groups (n=6 each), according to irrigation technique. Samples were scanned with micro-CT before instrumentation, after Ca(OH)2 filling, and after irrigation. Ca(OH)2 reduction in the coronal, middle, and apical thirds and in the isthmus were assessed with three-dimensional image analysis. Next, specimens were split longitudinally, and canal walls were examined with SEM for Ca(OH)2 residues. Data were statistically evaluated with the Kruskal-Wallis and Mann-Whitney tests (p=0.05). RESULTS: The PIPS and ultrasonic groups showed greater Ca(OH)2 reduction in the apical third and higher cleanliness of the isthmus than the EndoActivator and needle irrigation groups (p<0.05). Ca(OH)2 residue scores in the PIPS and ultrasonic groups were significantly lower than those in the EndoActivator and needle groups in all regions of the root canals (p<0.05). There was no significant difference between PIPS and ultrasonic groups (p>0.05), or between EndoActivator and needle groups (p>0.05). CONCLUSIONS: PIPS and ultrasonic irrigation more effectively removed Ca(OH)2 from the main canal and isthmus in maxillary premolars than did EndoActivator or needle irrigation.

Efficacy of 3 different irrigation systems on removal of calcium hydroxide from the root canal: a scanning electron microscopic study.

INTRODUCTION: The purpose of this study was to evaluate the effectiveness of different irrigation systems on removing calcium hydroxide (Ca[OH]2) from the root canal by using a scanning electron microscope. METHODS: Forty extracted single-rooted teeth were divided randomly into 4 groups. Canal instrumentation was done, and the teeth were filled with Ca(OH)2 paste. One week later, 4 techniques were used for Ca(OH)2 removal. In the first group, the canals were cleaned with a master apical file. The second, third, and fourth groups were irrigated using the EndoVac (Discus Dental, Culver City, CA), EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, OK), and ProUltra (Dentsply Tulsa, Tulsa, OK) systems, respectively. All the groups were irrigated with 3 mL (18%) EDTA and 3 mL (1%) NaOCl for 1 minute. The canal walls were viewed, and the remaining amount of Ca(OH)2 was evaluated using a scanning electron microscope. A scoring system was used to assess the amount of residue Ca(OH)2 on each third of the canal. The obtained data for comparisons between the conventional irrigation needle and each device were statistically analyzed using the Mann-Whitney U test. RESULTS: To compare the 4 devices, the results were statistically analyzed using the analysis of variance test. CONCLUSIONS: None of the investigated techniques removed the Ca(OH)2 dressing completely. However, the EndoActivator System showed better results in removing Ca(OH)2 in each third of the root canals in comparison with the other techniques.

Mineral trioxide aggregate (MTA) solubility and porosity with different water-to-powder ratios.

This study tested mineral trioxide aggregate (MTA) solubility and porosity with different water-to-powder proportions. The study also determined the chemical composition of the salts dissolved by MTA. Four sets of specimens using the following water-to-powder proportions were prepared: 0.26, 0.28, 0.30, and 0.33 grams of water per gram of cement. The latter is the ratio recommended by the manufacturer. It was determined that the degree of solubility and porosity increased as the water-to-powder ratio increased. Significant differences were found among the sets of specimens. The chemical analyses of the salts dissolved by MTA in the water identified the presence of calcium as the main chemical compound. The pH level of the solution was highly alkaline, ranging between 11.94 and 11.99. It can be stated that the calcium found in the solution should be in its hydroxide state at this high pH level. This ability to release calcium hydroxide could be of clinical significance because it could be related to the proven capacity of MTA to induce mineralization.

Determination of the p-monochlorophenol residue in the calcium hydroxide + P-monochlorophenol combination used as an intracanal dressing in pulpless teeth of dogs with induced chronic periapical lesion.

To determine the presence of p-monochlorophenol in the calcium hydroxide (Calen) + p-monochlorophenol combination after its use as intracanal dressing, periapical lesions were induced in 60 root canals of upper and lower premolars of four dogs. After biomechanical preparation, the root canals received the intracanal medication, which was removed from the apical third after 2, 4, 7, and 14 days for chemical analysis by spectrophotometry. The results showed a p-monochlorophenol loss of approximately 50.0% in the dressing after 48 h, with no further significant loss after longer periods of times. p-Monochlorophenol was still present in the medication after 14 days.

Diffusion of Ca(OH)2 associated with different vehicles: chromatographic study (high-performance liquid chromatography).

Using high-performance liquid chromatography (HPLC), small amounts of liquid samples in which 25 premolar human teeth were immersed were evaluated. Each tooth was immersed separately in 800-ml flasks with distilled ultra-pure deionized water and remained there for 1678 h after the filling of their canals with Ca(OH)2 associated with different vehicles: group 1: polyethylene glycol and colophon (Calen); group 2: glycerin and camphorated paramonochlorophenol; group 3: camphorated paramonochlorophenol; group 4: glycerin and tricresol formol; and group 5: anesthetic solution (Citanest). Five polyethylene tubes were filled with each of these pastes and placed unsealed in similar flasks. At the end of this period, HPLC analyses of the aqueous medium related to each group were performed to detect other substances that had diffused from the pastes used in the canals of the teeth other than calcium and hydroxyl ions. Although the groups presented different maximum peaks when there was no barrier, they all showed higher values than when the tooth was present. At least 15 substances other than Ca2+ and OH- were detected in the aqueous medium of group 4. Analyzing the HPLC graphs, we concluded that not only Ca2+ and OH-, but also a considerable quantity of other components of the pastes diffused through the dentine and reached the external root surface.

Emission spectroscopy for coal-fired cyclone furnace diagnostics.

Using a spectrograph and charge-coupled device (CCD) camera, ultraviolet and visible light emission spectra were obtained from a coal-burning electric utility's cyclone furnaces operating at either fuel-rich or fuel-lean conditions. The aim of this effort is to identify light emission signals that can be related to a cyclone furnace's operating condition in order to adjust its air/fuel ratio to minimize pollutant production. Emission spectra at the burner and outlet ends of cyclone furnaces were obtained. Spectra from all cyclone burners show emission lines for the trace elements Li, Na, K, and Rb, as well as the molecular species OH and CaOH. The Ca emission line is detected at the burner end of both the fuel-rich and fuel-lean cyclone furnaces but is not detected at the outlet ends of either furnace type. Along with the disappearance of Ca is a concomitant increase in the CaOH signal at the outlet end of both types of furnaces. The OH signal strength is in general stronger when viewing at the burner end rather than the exhaust end of both the fuel-rich and fuel-lean cyclone furnaces, probably due to high, non-equilibrium amounts of OH present inside the furnace. Only one molecular species was detected that could be used as a measure of air/fuel ratio: MgOH. It was detected at the burner end of fuel-rich cyclone furnaces but not detected in fuel-lean cyclone furnaces. More direct markers of air/fuel ratio, such as CO and O2 emission, were not detected, probably due to the generally weak nature of molecular emission relative to ambient blackbody emission present in the cyclone furnaces, even at ultraviolet wavelengths.

Characterization and aqueous extraction of calcium hydroxide materials.

Analysis of two single and eight dual product systems showed the former to be calcium hydroxide dispersed in an aqueous gel in methyl ethyl ketone solution of an acrylic polymer and the latter were cements based on the polymerization occurring when mixing salicylate esters with calcium hydroxide. Using water as an extractant under controlled conditions, specimens of the prepared materials produced marked differences in pH values over 24 hours and conductivity over 72 hours; also cumulative extractions over 26 weeks showed substantial variation in the amount of calcium hydroxide and other solubles.

Crystal induced arthritis: gout and pseudogout.

Intrasynovial deposits of monourate crystals in the presence of serum hyperuricaemia, and calcium pyrophosphate dihydrate (CPPD) crystals, are responsible for gout and pseudogout respectively. Identification of these by synovial fluid analysis is described. The clinical features, minimum investigations, history-taking, management and drug regimes of gout and pseudogout are discussed. Periodic review of the patient is stressed. Other intrasynovial crystals are briefly outlined.

Chemical analysis of the formation of calcium carbonate and its influence on calcium hydroxide pastes in connective tissue of the dog--Part II.

The objective of this research was to chemically analyze calcium hydroxide pastes added to three hydrosoluble vehicles having different acid-base characteristics by implanting polyethylene tubes in subcutaneous connective tissue in dogs, evaluating the formation of calcium carbonate over a period of 7, 30, 45, and 60 days. The three vehicles were saline, anesthetic, and polyethylene glycol 400. Determination of the formation of calcium carbonate was evaluated by volumetry of neutralization using hydrochloric acid for titration.

Comparative study of synthesised hyroxyapatite from pure chemicals and Malaysian natural limestone precursors.

Hydroxyapatite, (HA; Ca1O(PO4)6(OH)2) has been successfully applied in medical and dental applications for several years due to its excellent biocompatibility. The usage of HA in Malaysia, however, is limited due to the lack of availability. Therefore the aim of this work is to produce HA materials from both pure chemicals and from Malaysian natural limestone precursors, and to compare their bulk properties. However, parts of Malaysian natural limestone deposits actually consist of a combination of Ca(OH)2 and CaCO3. In order to utilise the limestone to produce HA material, the combination of these commercially pure chemicals as HA precursors should still work. In order to test this hypothesis, two HAs were produced by wet synthesis technique utilising (a) combination of Ca(OH)2 + CaCO3 from pure commercial chemicals [WCC] and (b) a local natural limestone [WL] precursors. The HAs produced; WCC and WL, were compacted into discs and sintered at 1250 degrees C. The characterisations and evaluations conducted were XRD, SEM-EDX, FTIR and shrinkage factor. The results indicate that WL gives slightly better bulk properties compared to WCC.