Influence of the Organic Matrix on Root Dentine Erosion by Citric Acid

2005 ◽  
Vol 39 (2) ◽  
pp. 134-138 ◽  
Author(s):  
A.T. Hara ◽  
M. Ando ◽  
J.A. Cury ◽  
M.C. Serra ◽  
C. González-Cabezas ◽  
...  
Keyword(s):  
Citric Acid ◽  
Organic Matrix

scholarly journals Viscosity controls humidity dependence of N<sub>2</sub>O<sub>5</sub> uptake to citric acid aerosol

2015 ◽  
Vol 15 (15) ◽  
pp. 21983-22011 ◽  
Author(s):  
G. Gržinić ◽  
T. Bartels-Rausch ◽  
T. Berkemeier ◽  
A. Türler ◽  
M. Ammann
Keyword(s):  
Citric Acid ◽  
Aerosol Particles ◽  
Organic Matrix ◽  
Oxidative Capacity ◽  
Uptake Kinetics ◽  
Kinetic Regime ◽  
Night Time ◽  
Polycarboxylic Acids ◽  
Humidity Dependence ◽  
The Impact

Abstract. The heterogeneous loss of dinitrogen pentoxide (N2O5) to aerosol particles has a significant impact on the night time nitrogen oxide cycle and therefore the oxidative capacity in the troposphere. Using a 13N short lived radioactive tracer method we studied the uptake kinetics of N2O5 on citric acid aerosol particles as a function of relative humidity (RH). The results show that citric acid exhibits lower reactivity than similar di- and polycarboxylic acids, with uptake coefficients between ~ 3 × 10−4–~ 3 × 10−3 depending on humidity (17–70 % RH). This humidity dependence can be explained by a changing viscosity and, hence, diffusivity in the organic matrix. Since the viscosity of highly concentrated citric acid solutions is not well established, we present four different parameterizations of N2O5 diffusivity based on the available literature data or estimates for viscosity and diffusivity. Above 50 % RH, uptake is consistent with the reacto-diffusive kinetic regime whereas below 50 % RH, the uptake coefficient is higher than expected from hydrolysis of N2O5 within the bulk of the particles, and the uptake kinetics may be limited by loss on the surface only. This study demonstrates the impact of viscosity in highly oxidized and highly functionalized secondary organic aerosol material on the heterogeneous chemistry of N2O5 and may explain some of the unexpectedly low loss rates to aerosol derived from field studies.

Preparation of Deep Hydrodesulfurzation Catalysts for Diesel Fuel using Organic Matrix Decomposition Method

2016 ◽  
pp. 216-253
Author(s):  
Hamid Audah AlMegren ◽  
Sergio Gonzalez-Cortes ◽  
Yu Huang ◽  
Haoyi Chen ◽  
Yangdong Qian ◽  
...  
Keyword(s):  
Citric Acid ◽  
Diesel Fuel ◽  
Decomposition Method ◽  
Performance Test ◽  
Chelating Agent ◽  
Matrix Decomposition ◽  
Organic Matrix ◽  
Hydrogen Consumption ◽  
Dispersing Agent ◽  
Before And After

In this work, a series of supported CoMo or NiMo HDS catalysts have been prepared based on the organic-metal matrix decomposition method and tested for diesel deep HDS with minimum hydrogen consumption under relatively low hydrogen partial pressure conditions. The aim is to develop a HDS catalyst which can reduce sulphur in diesel fuel from 5000ppm down to 50 ppm in a single pass with minimum hydrogen consumption under the conditions of 340oC, 35 bar, LHSV 1.2 h-1 with low H2/oil ratio. The catalysts preparation process was monitored and the resultant catalyst samples before and after the HDS performance test have been characterised, some interesting results have been obtained. The presence of citric acid as organic additive/dispersing agent/chelating agent in the impregnation solution improved HDS activity compared to the equivalent CoMo catalyst prepared without citric acid, The order of activity of the cobalt precursors is Co citrate > Co acetate > Co nitrate.

Profilometric Quantification of Erosive Tissue Loss in Dentine: A Systematic Evaluation of the Method

2016 ◽  
Vol 50 (5) ◽  
pp. 443-454 ◽  
Author(s):  
Nadine Schlueter ◽  
Katja Jung ◽  
Carolina Ganss
Keyword(s):  
Citric Acid ◽  
Organic Matrix ◽  
Tissue Loss ◽  
Systematic Evaluation ◽  
Measuring Device ◽  
Matrix Shrinkage ◽  
Mineral Status ◽  
Measurement Results ◽  
Matrix Removal ◽  
Criterion Matrix

Profilometry is established in erosion research. However, in the case of dentine, factors such as the demineralised organic matrix, desiccation effects, or type of measuring device may have an impact on the measurement results, which were investigated in the present study. Dentine specimens were eroded with citric acid (1%, pH 2.6) for 5, 10, 15, 20, 30, 60, 90, and 120 min (n = 15 each). For each specimen, tissue loss was determined under various conditions - before/after enzymatic matrix removal, under standardised wet and desiccated (2/10 min) conditions - with non-contact and contact profilometry. In the presence of matrix, under wet conditions, non-contact profilometry revealed almost no tissue loss. Values (mean ± SD) ranged between 0.3 ± 0.7 µm (5 min) and 3.4 ± 1.5 µm (120 min). Contact profilometry increased values significantly (range: 2.9 ± 1.1 to 30.6 ± 5.8 µm). Desiccation (2 min) significantly increased values, except for 5 min of demineralisation, for non-contact profilometry (range: 0.8 ± 1.3 to 22.1 ± 5.5 µm), and decreased values for contact profilometry up to 15 min and increased them as from 90 min (range: 0.9 ± 1.2 to 33.0 ± 5.5 µm); results after 10 min of desiccation were comparable. After the removal of matrix, under wet conditions, values were distinctly higher (non-contact: 3.5 ± 0.8-55.5 ± 7.4 µm; contact: 4.2 ± 1.3-57.8 ± 8.1 µm). Desiccation (10 min) lowered values by about 2-5 µm due to specimen deformation. Bland-Altman comparisons of various outcomes revealed distinct significant proportional and relative biases. Loss of mineralised tissue cannot be adequately quantified in the presence of matrix. Desiccation leads to matrix shrinkage and specimen deformation. Most importantly, tissue loss values obtained in the presence or absence of matrix are not proportional. Therefore, if mineral status is the target criterion, matrix removal and moisture control are prerequisites.

The Impact of the Demineralized Organic Matrix on the Effect of TiF4 Varnish on the Progression of Dentin Erosive Loss

2017 ◽  
Vol 51 (3) ◽  
pp. 264-270 ◽  
Author(s):  
Beatriz Martines de Souza ◽  
Mariele Vertuan ◽  
Marília Afonso Rabelo Buzalaf ◽  
Ana Carolina Magalhães
Keyword(s):  
Citric Acid ◽  
Artificial Saliva ◽  
In Vitro Study ◽  
Organic Matrix ◽  
Analysis Data ◽  
Acid Ph ◽  
Bonferroni Test ◽  
And Control ◽  
The Impact

This in vitro study compared the effect of TiF4 varnish with that of NaF varnish, applied on pre-eroded bovine dentin samples, with respect to the progression of erosive loss, in the presence or absence of the demineralized organic matrix (DOM). One hundred and sixty bovine dentin samples were pre-eroded (0.1% citric acid, pH 2.5, 30 min). Half of the samples were subjected to the DOM removal (collagenase solution, 5 days). Samples with and without the DOM were treated according to the groups (n = 20 with DOM and 20 without DOM/group): TiF4 varnish (2.45% F), NaF varnish (2.45% F), placebo varnish (without fluoride) and control (no treatment). Thereafter, the treated samples were submitted to erosive challenges 4 × 90 s/day (0.1% citric acid, pH 2.5) during 7 days. Between the challenges, the samples were immersed in artificial saliva. The dentin erosive loss was measured using contact profilometry (µm, n = 15). Five dentin samples per group were prepared for energy-dispersive X-ray spectroscopy analysis. Data were compared using 2-way ANOVA/Bonferroni test (p < 0.05). Both fluoride varnishes were effective in reducing the erosive loss progression regardless of the dentin condition when compared to placebo varnish and control groups. Despite the fact that the TiF4 varnish was more effective than the NaF varnish for both dentin conditions (p < 0.001), its effect was significantly reduced in the absence of DOM (p < 0.05). It can be concluded that the TiF4 varnish is the best treatment in reducing the progression of dentin erosive loss (100%) in vitro, but its protective effect is more pronounced in the presence of DOM.

scholarly journals Viscosity controls humidity dependence of N<sub>2</sub>O<sub>5</sub> uptake to citric acid aerosol

2015 ◽  
Vol 15 (23) ◽  
pp. 13615-13625 ◽  
Author(s):  
G. Gržinić ◽  
T. Bartels-Rausch ◽  
T. Berkemeier ◽  
A. Türler ◽  
M. Ammann
Keyword(s):  
Citric Acid ◽  
Aerosol Particles ◽  
Organic Matrix ◽  
Oxidative Capacity ◽  
Uptake Kinetics ◽  
Kinetic Regime ◽  
Night Time ◽  
Polycarboxylic Acids ◽  
Humidity Dependence ◽  
The Impact

Abstract. The heterogeneous loss of dinitrogen pentoxide (N2O5) to aerosol particles has a significant impact on the night-time nitrogen oxide cycle and therefore the oxidative capacity in the troposphere. Using a 13N short-lived radioactive tracer method, we studied the uptake kinetics of N2O5 on citric acid aerosol particles as a function of relative humidity (RH). The results show that citric acid exhibits lower reactivity than similar dicarboxylic and polycarboxylic acids, with uptake coefficients between ∼ 3 × 10-4–∼ 3 × 10-3 depending on humidity (17–70 % RH). At RH above 50 %, the magnitude and the humidity dependence can be best explained by the viscosity of citric acid as compared to aqueous solutions of simpler organic and inorganic solutes and the variation of viscosity with RH and, hence, diffusivity in the organic matrix. Since the diffusion rates of N2O5 in highly concentrated citric acid solutions are not well established, we present four different parameterizations of N2O5 diffusivity based on the available literature data or estimates for viscosity and diffusivity of H2O. Above 50 % RH, uptake is consistent with the reacto-diffusive kinetic regime whereas below 50 % RH, the uptake coefficient is higher than expected from hydrolysis of N2O5 within the bulk of the particles, and the uptake kinetics is most likely limited by loss on the surface only. This study demonstrates the impact of viscosity in highly oxidized and highly functionalized secondary organic aerosol material on the heterogeneous chemistry of N2O5 and may explain some of the unexpectedly low loss rates to aerosol derived from field studies.

A Protozoan Model for Golgi-Associated Calcification

1971 ◽  
Vol 29 ◽  
pp. 332-333
Author(s):  
D. C. Williams ◽  
D. E. Outka
Keyword(s):  
Golgi Apparatus ◽  
Organic Matrix ◽  
Model System ◽  
Sequential Formation

Many studies have shown that the Golgi apparatus is involved in a variety of synthetic activities, and probably no Golgi product is more elaborate than the scales produced by various kinds of phytoflagellates. The formation of calcified scales (coccoliths, Fig. 1,2) of the coccolithophorid phytoflagellates provides a particularly interesting model system for the study of biological mineralization, and the sequential formation of Golgi products.The coccoliths of Hymenomonas carterae consist of a scale-like base (Fig. 2 and 4, b) with a highly structured calcified (CaCO3) rim composed of two distinct elements which alternate about the base periphery (Fig. 1 and 3, A, B). Each element is enveloped by a sheath-like organic matrix (Fig. 3; Fig. 4, m).

Human Enamel Replication

1976 ◽  
Vol 34 ◽  
pp. 180-181
Author(s):  
Norman L. Dockum ◽  
John G. Dockum
Keyword(s):  
Organic Matrix ◽  
Human Teeth ◽  
Human Enamel ◽  
Straight Line ◽  
Ultrastructural Characteristics

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.

A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

1992 ◽  
Vol 50 (2) ◽  
pp. 1024-1025
Author(s):  
Jun Liu ◽  
Katie E. Gunnison ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Ion Beam ◽  
Laminated Composite ◽  
Organic Matrix ◽  
Pearl Oyster ◽  
Interfacial Structure ◽  
Interfacial Region ◽  
Thin Sections ◽  
Organic Layers ◽  
Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

Coadministration of citric acid allows oxytetracycline dose reduction in yellowtail Seriola quinqueradiata infected with Vibrio anguillarum

2020 ◽  
Vol 140 ◽  
pp. 25-29
Author(s):  
K Akiyama ◽  
N Hirazawa ◽  
A Hatanaka
Keyword(s):  
Body Weight ◽  
Citric Acid ◽  
Effective Treatment ◽  
Dose Reduction ◽  
Vibrio Anguillarum ◽  
Enhancing Effect ◽  
Bacterial Diseases ◽  
Seriola Quinqueradiata ◽  
Poor Efficacy

Oxytetracycline (OTC) has been commonly used as an effective antibiotic against various fish bacterial diseases, including vibriosis. In this study, the absorption-enhancing effect of citric acid on oral OTC pharmacokinetics and treatment of artificial Vibrio anguillarum infection was evaluated in juvenile yellowtail Seriola quinqueradiata followed by serum OTC concentration analysis. When 25 mg kg-1 body weight (BW) OTC was administered in combination with 1250 mg kg-1 BW citric acid, the serum OTC concentration reached almost the same concentration as that of the group treated with 50 mg kg-1 BW OTC. This coadministration successfully suppressed mortality due to vibriosis similar to the group treated with 50 mg kg-1 BW OTC. Conversely, poor efficacy was observed when only 25 mg kg-1 BW OTC was administered. These results suggest that coadministration of citric acid can be beneficial in reducing the dose of OTC needed for effective treatment, and thus contributes to the goal of reduced use of this antibiotic in aquaculture.

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