scholarly journals Effect of acid pretreatment of the silica substrate on the stability of octadecyl modified reversed phases

1990 ◽  
Vol 29 (9-10) ◽  
pp. 473-481 ◽  
Author(s):  
M. Hetem ◽  
J. de Haan ◽  
H. Claessens ◽  
Ph. Mussche ◽  
C. Cramers
Keyword(s):  
Acid Pretreatment ◽  
Silica Substrate ◽  
The Stability ◽  
Reversed Phases

scholarly journals Evaluation on the Stability of Amine-Mesoporous Silica Adsorbents used for CO2 Capture

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Dang Viet Quang ◽  
Dao Van Duong ◽  
Vu Thi Hong Ha ◽  
Dao Sy Duc ◽  
Tran Thi Ngoc Dung ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Co2 Capture ◽  
Capture Process ◽  
Silica Substrate ◽  
Humid Condition ◽  
Silica Adsorbents ◽  
Reduction Of Energy Consumption ◽  
The Stability ◽  
Co2 Adsorption Capacity ◽  
Co2 Capture Capacity

Amine-mesoporous silica has been considered as a promising CO2 adsorbent with high potential for the reduction of energy consumption and CO2 capture cost; however, its stability could greatly vary with synthetic method. In this study, adsorbents prepared by impregnating different amines including polyethylenimine (PEI) and 3-aminopropyltriethoxysilane (APTES) onto mesoporous silica were used to evaluate the effect of amines selection on the stability of adsorbents used in CO2 capture process. Results revealed that APTES impregnated mesoporous silica (APTES-MPS) is more stable than PEI-impregnated mesoporous silica (PEI-MPS); APTES-MPS was thermally decomposed at ≈280 oC, while PEI-MPS was thermally decomposed at ≈180 oC only. PEI-MPS was particularly less stable when operating under dry condition; its CO2 adsorption capacity reduced by 22.1% after 10 adsorption/regeneration cycles, however, the capacity can be significantly improved in humid condition. APTES-MPS showed a greater stability with no significant reduction in CO2 capture capacity after 10 adsorption/regeneration cycles. In general, APTES-MPS adsorbent possesses a higher stability compared to PEI-MPS thanks to the formation of chemical bonds between amino-functional groups and mesoporous silica substrate. Keywords: Mesoporous silica; CO2 capture; Adsorption; Regeneration; Emission.

Effect of Acid Pretreatment on the Stability of EDTA, Cysteine, Lactic and Succinic Acid Complexes of Various Iron Sources in a Wheat Flake Cereal

1987 ◽  
Vol 50 (7) ◽  
pp. 587-597
Author(s):  
D. B. NADEAU ◽  
F. M. CLYDESDALE
Keyword(s):  
Succinic Acid ◽  
Ferrous Sulfate ◽  
Iron Complex ◽  
Molar Ratio ◽  
Acid Pretreatment ◽  
Gastrointestinal Ph ◽  
Iron Solubilization ◽  
The Stability ◽  
Reducing Potential

An in vitro incubation at pH 2 of EDTA, cysteine, lactic or succinic acids with each of five iron sources, [hydrogen (HRI) and electrolytically reduced elemental iron (ERI), ferric chloride (FeCl3), ferrous sulfate (FeSO4) and ferric orthophosphate (FOP)] at a 10:1 molar ratio (ligand:iron) was evaluated for its effect on iron solubilization in a wheat flake cereal subjected to a sequential gastrointestinal pH treatment from endogenous pH (E) to 2 to 6. Incubation significantly enhanced the iron solubilizing potential of EDTA at each pH with HRI and ERI, while lactic and succinic acids were similarly effective with FeSO4 and FeCl3 at pH 2. The reducing potential of cysteine, along with its role as a ligand, generated substantial amounts of Fe+ 2 (pH 2) at the apparent expense of complexed iron. However, with the exception of ERI (pH E), incubation did not increase cysteine's effectiveness in producing more soluble iron (ionic + complexed). This indicates that pH was the major solubilizing factor. Due to FOP's relative insolubility, incubation proved ineffective in all instances. These in vitro results indicate that acid incubation to form a ligand-iron complex has the potential to improve bioavailability of iron.

An Investigation Concerning the Stability of a Sterically Protected Cyanopropyl Modified Silica Substrate

1994 ◽  
Vol 17 (1) ◽  
pp. 49-68 ◽  
Author(s):  
A. Houbenová ◽  
H. A. Claessens ◽  
J. W. de Haan ◽  
C. A. Cramers ◽  
K. Stulík
Keyword(s):  
Modified Silica ◽  
Silica Substrate ◽  
The Stability

scholarly journals Influence of alkyl chain length on the stability of n-alkyl-modified reversed phases. 2. Model dissolution study

1990 ◽  
Vol 62 (21) ◽  
pp. 2296-2300 ◽  
Author(s):  
Martin J. J. Hetem ◽  
Jan W. De Haan ◽  
Henk A. Claessens ◽  
Leo J. M. Van de Ven ◽  
Carel A. Cramers ◽  
...  
Keyword(s):  
Chain Length ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Dissolution Study ◽  
The Stability ◽  
Reversed Phases

Influence of alkyl chain length on the stability of n-alkyl-modified reversed phases. 1. Chromatographic and physical analysis

1990 ◽  
Vol 62 (21) ◽  
pp. 2288-2296 ◽  
Author(s):  
Martin J. J. Hetem ◽  
Jan W. De Haan ◽  
Henk A. Claessens ◽  
Leo J. M. Van de Ven ◽  
Carel A. Cramers ◽  
...  
Keyword(s):  
Chain Length ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Physical Analysis ◽  
The Stability ◽  
Reversed Phases

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

Uniformity of Magnification from Different Electron Microscopes

1967 ◽  
Vol 25 ◽  
pp. 32-33
Author(s):  
Godfrey C. Hoskins ◽  
V. Williams ◽  
V. Allison
Keyword(s):  
Diffraction Grating ◽  
The Other ◽  
Carbon Replica ◽  
Electron Microscopes ◽  
The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

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