A re-examination of churchite

1953 ◽  
Vol 30 (223) ◽  
pp. 211-217 ◽  
Author(s):  
G. F. Claringbull ◽  
Max H. Hey
Keyword(s):  
Molecular Weight ◽  
Rare Earths ◽  
Quantitative Data ◽  
Hydrated Phosphate ◽  
Mean Molecular Weight ◽  
Cerium Group

In the course of a study of certain cerium minerals, a spectrogram of churchite was taken and it was noticed that the cerium lines were barely visible, whereas the yttrium lines were very strong. We therefore decided to re-investigate this species.Churchite was originally described by A. H. Church in 1865, and named by C. G. Williams in the same year. The specimens were collected by R. Talling from an unnamed locality in Cornwall. It has only been analysed once, by Church, who showed it to be a hydrated phosphate of rare-earths and lime; his quantitative data have been recalculated and included in table I. Church obtained qualitative reactions for the cerium group of rare-earths, and for cerium itself, but made no attempt to determine the ratio of cerium to yttrium earths; he assumed a mean molecular weight for the rare-earths which would correspond to R2O3 324, essentially a mixture of cerium earths with but little yttria, but did not adduce any evidence for this assumption.

HES 200/0.5 Is not HES 200/0.5

1995 ◽  
Vol 74 (06) ◽  
pp. 1452-1456 ◽  
Author(s):  
Johannes Treib ◽  
Anton Haass ◽  
Gerhard Pindur ◽  
Ulrich T Seyfert ◽  
Wolfgang Treib ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hydroxyethyl Starch ◽  
Clinical Relevance ◽  
Dilution Effect ◽  
Repeated Administration ◽  
Plasma Viscosity ◽  
Degree Of Substitution ◽  
Pronounced Increase ◽  
Large Molecules ◽  
Mean Molecular Weight

SummaryThe plasma clearance of hydroxyethyl starch (HES) depends on the initial molecular weight and the degree of substitution. So far, little attention has been paid to the clinical relevance of the C2/C6 substitution ratio of hydroxyethyl starch.10 patients with cerebrovascular circulatory disturbance received hemodilution therapy for 10 days, consisting of 10% HES 200/0.5 (mean molecular weight 200 kD, degree of substitution 0.5) with a C2/C6 ratio of 13.4. A second group of 10 patients received a starch solution with identical initial molecular weight and degree of substitution but with a C2/C6 ratio of 5.7.After the administration of a single dose, no significant differences between the two groups were observed. After repeated administration, significant differences could be detected in hemorheology, coagulation and elimination (p<0.01). The larger C2/C6 ratio led to a higher intravascular mean molecular weight (95 vs. 84 kD), which in turn led to a higher increase in serum concentration during the therapy (14.7 vs.8.6 mg/ml). Hematocrit was lowered more (-30,5 vs. -23,5%) and plasma viscosity was increased more. There was also a more pronounced increase in partial thromboplastin time (+30% vs. +13%) and a factor of 2 larger decrease of factor VIII/von Willebrand factor-complex (p <0.01), which exceeded the dilution effect.The higher C2/C6 ratio of HES 200/0.5/13.4 slows down enzymatic degradation. After repeated administration of this starch, large molecules accumulate which are inefficiently degraded. The same effect has been observed after therapy with highly-substituted HES. This accumulation of large molecules leads to a beneficial longer lasting volume effect. The disadvantages include an increase in plasma viscosity and coagulation disturbances, which cannot be explained with the respective dilution effect alone. For these reasons, the C2/C6 ratio is of clinical relevance and should be included in the product labeling in the future.

Suppressive Effect of Dextran on Platelet Adhesiveness

1966 ◽  
Vol 16 (03/04) ◽  
pp. 384-394 ◽  
Author(s):  
S Cronberg ◽  
B Robertson ◽  
Inga Marie Nilsson ◽  
J.-E Niléhn
Keyword(s):  
Molecular Weight ◽  
Bleeding Time ◽  
Slight Modification ◽  
Molecular Size ◽  
Suppressive Effect ◽  
Factor Ix ◽  
Factor V ◽  
Platelet Adhesiveness ◽  
History Of ◽  
Mean Molecular Weight

Summary43 normal volunteers, 3 patients with thrombophlebitis, and 1 patient with a high platelet adhesiveness and a history of thrombophlebitis have received dextran and its action on the mechanism of haemostasis has been studied. Platelet adhesiveness has been investigated by a slight modification of Hellem’s methods for whole blood and plasma. Dextran with a mean molecular weight of 70,000 produced a markedly lowered platelet adhesiveness together with a moderate prolongation of the Ivy bleeding time. Factor VIII was decreased by about 50% and factor V, factor IX and fibrinogen were decreased slightly more than could be expected from haemodilution alone. No fibrinolysis occurred. Dextran of lower molecular size was less potent. The possible use of dextrans as a thrombosis prophylactic agent is discussed.

STUDIES ON THE ANTITHROMBOTIC ACTION OF A LOW MOLECULARWEIGHT HEPARIN OBTAINED FROM BEEF MUCOSAL ORIGIN AND PEROXIDATIVE CLEAVAGE

1987 ◽  
Author(s):  
P Bianchini ◽  
R Nonn ◽  
J Fareed ◽  
J M Walenga ◽  
A Kumar
Keyword(s):  
Molecular Weight ◽  
Structural Integrity ◽  
Factor Xa ◽  
Inhibitory Effects ◽  
Heparin Cofactor Ii ◽  
At Iii ◽  
Antithrombotic Effects ◽  
In Vitro Systems ◽  
Mean Molecular Weight

We have studied a low molecular weight heparin (LMWH) obtained by acontrolled peroxidative depolymerization of beef mucosal heparin (OP 2123, Opocrin, Corlo, Italy). This product was found to be significantly different from other LMWHs in that it exhibits the same COO-/SO2- ratios as unfractionated heparin, contains reducing end groups composed of 2-sulfated iduronic acid or 6-disulfated glucosamine and retains an identical structural integrity as that of native heparin. As opposed to most other LMWHs the oligosaccharide components of OP 2123 consist of homogeneous progressive units. In addition, the relative amount of AT-IIIaffinity components in OP 2123 were 20-30% less than other LMWHs. OP 2123 has a mean molecular weight of 6200 daltons with a potency of 90 anti-factor Xa U/mg and 68 USP U/mg. This agent produced strong antithrombotic actions in a rabbit stasis model against both an activated prothrombin complex and a prothrombin complex concentrate/Russell's viper venomcombination (ED50:(IV) 30-70 ug/kg;(SC) 0.6-1.5 mg/kg). The antithrombotic effects were comparable to other LMWHs in normal rabbits: however, in AT III depleted rabbits (immunodepleted and y thrombin depleted), OP 2123 produced stronger antithrombotic effects than most other LMWHs. The in vitro systems in contrast to other LMWHs, CP 2123 produced stronger inhibitory effects in AT III depleted plasma as measured by fibrinopeptide A generation and amidolytic anti-factor Xa and anti-factor Ila methods. The relative heparin cofactor II activity as measured by amidolytic method was also found to be higher than with most LMWHs. These results suggest that OP 2123, unlike most LMWHs, non AT III mediated actions play a major role in themendiation of the antithrombotic actions.

scholarly journals Properties of sub-Neptune atmospheres: TOI-270 system

2020 ◽  
Vol 495 (1) ◽  
pp. 962-970
Author(s):  
J Chouqar ◽  
Z Benkhaldoun ◽  
A Jabiri ◽  
J Lustig-Yaeger ◽  
A Soubkiou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Signal To Noise Ratio ◽  
Spectral Features ◽  
Transmission Spectra ◽  
Infrared Transmission ◽  
Signal To Noise ◽  
Space Telescope ◽  
Molecular Features ◽  
James Webb Space Telescope ◽  
Mean Molecular Weight

ABSTRACT We investigate the potential for the James Webb Space Telescope (JWST) to detect and characterize the atmospheres of the sub-Neptunian exoplanets in the TOI-270 system. Sub-Neptunes are considered more likely to be water worlds than gas dwarfs. We model their atmospheres using three atmospheric compositions – two examples of hydrogen-dominated atmospheres and a water-dominated atmosphere. We then simulate the infrared transmission spectra of these atmospheres for JWST instrument modes optimized for transit observation of exoplanet atmospheres: NIRISS, NIRSpec, and MIRI. We then predict the observability of each exoplanet’s atmosphere. TOI-270c and d are excellent targets for detecting atmospheres with JWST transmission spectroscopy, requiring only 1 transit observation with NIRISS, NIRSpec, and MIRI; higher signal-to-noise ratio can be obtained for a clear H-rich atmosphere. Fewer than three transits with NIRISS and NIRSpec may be enough to reveal molecular features. Water-dominated atmospheres require more transits. Water spectral features in water-dominated atmospheres may be detectable with NIRISS in two or three transits. We find that the detection of spectral features in a cloudy, H-rich atmosphere does not require integrations as long as those required for the water-dominated atmosphere, which is consistent with the differences in atmospheric mean molecular weight. TOI-270c and d could be prime targets for JWST transit observations of sub-Neptune atmospheres. These results provide useful predictions for observers who may propose to use JWST to detect and characterize the TOI-270 planet atmospheres.

scholarly journals A QUANTITATIVE THEORY OF THE PRECIPITIN REACTION

1937 ◽  
Vol 66 (2) ◽  
pp. 251-272 ◽  
Author(s):  
Herbert E. Stokinger ◽  
Michael Heidelberger
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Quantitative Data ◽  
Mass Action ◽  
Law Of Mass Action ◽  
Quantitative Theory ◽  
Precipitin Reaction ◽  
Thyroglobulin Antibody ◽  
Molecular Ratios ◽  
Antibody Excess

1. Quantitative data for both homologous and heterologous precipitin reactions of human, hog, beef, and sheep thyroglobulins show that these reactions have the same mechanism as other instances of the precipitin reaction and may be expressed quantitatively by the same equations derived from the law of mass action. 2. It is shown that all of the added antigen is precipitated in the region of antibody excess and in the equivalence zone, so that in these portions of the reaction range the composition of the specific precipitate may be calculated from the nitrogen precipitated and the amount of antigen nitrogen added. 3. The thyroglobulin-antibody reaction is characterized by low antibody N to antigen N ratios, as would be expected with an antigen of high molecular weight. Molecular ratios varying from 60:1 to 1:1 were calculated for the extremes of the reaction range, indicating a very large number of immunologically reactive groupings on the thyroglobulin molecule. 4. Failure of thyroxine or diiodotyrosine to inhibit specific precipitation was confirmed, but it is shown that this need not mean that these substances do not occur in thyroglobulin, as has been claimed.

Study of the Preparation and Degradable Characteristics of CaCO3-PE Film

2012 ◽  
Vol 499 ◽  
pp. 85-89
Author(s):  
Xue Yong Zhou ◽  
Xiang Yun Liu ◽  
Lei Lu ◽  
Lei Gu ◽  
Jing Jing Liu
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Ultraviolet Light ◽  
Light Irradiation ◽  
Breaking Elongation ◽  
Average Tensile Strength ◽  
Ultraviolet Light Irradiation ◽  
Filling Method ◽  
The Mean ◽  
Mean Molecular Weight

The CaCO3-polyethylene (PE) film was prepared by filling method, and the filling amount of calcium carbonate in film was 20%(w/w). The effects of natural weathering, ultraviolet light irradiation on the tensile strength, breaking elongation and molecular weight of the CaCO3-PE film was investigated comparing with the photosensitizer-PE film. After being located in the open air for 30 d, the average tensile strength, average breaking elongation and the mean molecular weight of CaCO3-PE film decreased 80.6%, 99.3% and 25.3%, respectively, as for the photosensitizer-PE film, the corresponding items decreased 18.8%, 45.0% and 11.7%, respectively. After ultraviolet light irradiation for 120 h, the average tensile strength of CaCO3-PE film decreased 29.9%, the average tensile strength of the photosensitizer-PE film, however, increased 20.5%. The average breaking elongation of CaCO3-PE film and photosensitizer-PE film decreased 97.3% and 84.1% respectively, the mean molecular weight of both films decreased 66.7% and 26.6% respectively. After covered by soil for 200 d, the weight loss of the CaCO3-PE film and photosensitizer-PE was 2.15% and 0.22%, respectively. The results showed that the degradability of CaCO3-PE film is superior to the photosensitizer-PE film.

Chlorinated Rubber and Nitrogenous Plasticizers. I. Viscosity of Mixtures of Chlorinated Rubber and Anhydroformaldehyde Urethan

1957 ◽  
Vol 30 (1) ◽  
pp. 274-282
Author(s):  
Michele Giua ◽  
Corrado Mancini
Keyword(s):  
Molecular Weight ◽  
Molecular Weights ◽  
Mixed Solutions ◽  
Quantitative Basis ◽  
The Mean ◽  
Mean Molecular Weight

Abstract The viscosities of solutions of chlorinated rubber in chloroform and in toluene and of mixed solutions of chlorinated rubber and anhydroformaldehyde urethan in toluene were measured. From the data it was possible to determine in an approximate way the mean molecular weight of chlorinated rubber and the mean molecular weights, determined viscometrically, of the mixtures. From the results it was, in turn, possible to derive the α coefficient in the relation of Kuhn. The action of anhydroformaldehyde urethan on chlorinated rubber could then be considered on a quantitative basis.

Sign in / Sign up

Export Citation Format

Share Document