Determination of the Gelation Time in Diluted Sols

MICC 90 ◽  
1991 ◽  
pp. 401-411
Author(s):  
Andrey I. Koltakov ◽  
Pavel G. Kudryavtsev
Keyword(s):  
1989 ◽  
Vol 43 (5) ◽  
pp. 821-826
Author(s):  
Haruki Oishi ◽  
Yasumichi Hatayama ◽  
Masaji Fusamoto ◽  
Yoshitsugu Sakata

A turbidimetric-kinetic photometer which monitors 64 samples simultaneously and independently has been developed for the automated measurement of endotoxin. This instrument measures the turbidity change at 660 nm in a gelation reaction of the LAL/endotoxin system and automatically scores the reaction time required to obtain a certain turbidity change as gelation time. Since a stationary dry bath incubator controls the reaction temperature of the samples at 37 ± 0.5°C and also controls the ambience of the optical system assembled into the incubator, the objective detection of gelation is provided without any disturbance from sample vibration, and the drift of the detection system is minimized. An extremely wide range for the calibration curve, such as 4 or 5 orders of magnitude of endotoxin concentration, is obtained without sample dilution. The coefficients of variation of the calculated endotoxin concentration are 4.91 to 14.0%.


1997 ◽  
Vol 13 (3) ◽  
pp. 186-191 ◽  
Author(s):  
Hiroshi Murata ◽  
John F. McCabe ◽  
Nicholas J. Jepson ◽  
Taizo Haxnada
Keyword(s):  

2021 ◽  
Vol 87 (2) ◽  
pp. 37-47
Author(s):  
Оlga Titova ◽  
Zoia Hrushak ◽  
Tetiana Kravchuk ◽  
Valerii Yefymenko ◽  
Mariia Maksumiuk

Purpose: The purpose of this article is to determine the dependence of the rate of gel formation on the type of reagent-inhibitor of the gel formation process, and to study the kinetic dependences of gel formation of silicate compositions in the presence of compounds that regulate the rate of gel formation. Research methods: Direct and reverse titration, potentiometric titration, pH-metry, determination of the dynamic viscosity on a rotational viscometer, axial compression method to determine the elastic modulus were used to study the possibility of using chemical reagents as gelation inhibitors. Results: The possibility of using inorganic and organic additives to slow down the gel formation process and the effect of these additives on the strength of the gel, their thermodynamic parameters have been researched. Discussion: The adding of organic acids into the silicate composition as "crosslinking agents" slows down the gel formation process, while replacing hydrochloric acid with other gel acids that slow down the gel formation process does not lead to a decrease in the strength characteristics of these systems compared to the standard. It was found that with an increase in the gelation time, the strength of the gels decreases, and the syneresis increases; the adding of inhibitor additives insignificantly worsens the filterability of silicate compositions, which in general have bad filterability, leading to an increase in resistance during filtration at the inlet section of the sample. Observations have shown that the addition of additives-inhibitors does not affect the thermal stability of gels, regardless of the additives' nature.


2008 ◽  
Vol 587-588 ◽  
pp. 27-31 ◽  
Author(s):  
M.J. Moura ◽  
M.M. Figueiredo ◽  
M. Helena Gil

This paper investigates the rheological behaviour of chitosan solutions crosslinked with different concentrations of genipin at body temperature and physiological pH. The effect of the crosslinker concentration on the rheological properties of hydrogels was evaluated. The oscillatory time sweep was used to analyze the dynamics of G’ during in situ gelation experiments enabling the determination of the gelation time. Additionally, the stress and frequency sweeps were employed to measure G’ of cured hydrogels. The solutions of chitosan crosslinked with genipin at physiological conditions were found to form relatively strong elastic gels for all the concentrations, when compared to pure chitosan. A significant reduction on gelation time was achieved. This behaviour shows that these formulations are able to be produced in situ and thus constitute promising matrices for cells and bioactive molecules encapsulation.


1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.


1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.


1961 ◽  
Vol 13 ◽  
pp. 29-41
Author(s):  
Wm. Markowitz
Keyword(s):  

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).


1972 ◽  
Vol 1 ◽  
pp. 27-38
Author(s):  
J. Hers

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.


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