scholarly journals Average molecular weight of surfactants in aerosols

2007 ◽  
Vol 7 (5) ◽  
pp. 13805-13838 ◽  
Author(s):  
M. T. Latif ◽  
P. Brimblecombe
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Atmospheric Aerosols ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Weight Fraction ◽  
Ozone Exposure ◽  
Before And After ◽  
Fine Mode ◽  
Active Substances

Abstract. Surfactants in atmospheric aerosols determined as methylene blue active substances (MBAS) and ethyl violet active substances (EVAS). The MBAS and EVAS concentrations can be correlated with surface tension as determined by pendant drop analysis. The effect of surface tension was more clearly indicated in fine mode aerosol extracts. The concentration of MBAS and EVAS was determined before and after ultrafiltration analysis using AMICON centrifuge tubes that define a 5000 Da (5 K Da) nominal molecular weight fraction. Overall, MBAS and to a greater extent EVAS predominates in fraction with molecular weight below 5 K Da. In case of aerosols collected in Malaysia the higher molecular fractions tended to be a more predominant. The MBAS and EVAS are correlated with yellow to brown colours in aerosol extracts. Further experiments showed possible sources of surfactants (e.g. petrol soot, diesel soot) in atmospheric aerosols to yield material having molecular size below 5 K Da except for humic acid. The concentration of surfactants from these sources increased after ozone exposure and for humic acids it also general included smaller molecular weight surfactants.

scholarly journals Cloud condensation nuclei properties of model and atmospheric HULIS

2006 ◽  
Vol 6 (1) ◽  
pp. 1073-1120 ◽  
Author(s):  
E. Dinar ◽  
I. Taraniuk ◽  
E. R. Graber ◽  
S. Katsman ◽  
T. Moise ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Fulvic Acid ◽  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Average Molecular Weight ◽  
Water Soluble ◽  
Number Average Molecular Weight ◽  
Secondary Sources ◽  
Multifunctional Compounds

Abstract. Humic like substances (HULIS) have been identified as a major fraction of the organic component of atmospheric aerosols. These large multifunctional compounds of both primary and secondary sources are surface active and water soluble. Hence, it is expected that they could affect activation of organic aerosols into cloud droplets. We have compared the activation of aerosols containing atmospheric HULIS extracted from fresh and slightly aged smoke particles and from daily pollution particles to activation of size fractionated fulvic acid from an aquatic source (Suwannee River fulvic acid), and correlated it to the estimated molecular weight and measured surface tension. A correlation was found between CCN-activation diameter of SRFA fractions and number average molecular weight of the fraction. The lower molecular weight fractions activated at lower critical diameters, which is explained by the greater number of solute species in the droplet with decreasing molecular weight. The three aerosol-extracted HULIS samples activated at lower diameters than any of the size-fractionated or bulk SRFA. By considering estimated number average molecular weight (MN), measured surface tension (ST) and activation diameters, the Köhler model was found to account for activation diameters, provided that accurate physico-chemical parameters are known.

Some Osmotic Measurements of the Molecular Weight of a High Molecular-Weight Fraction of Rubber Hydrocarbon

1955 ◽  
Vol 28 (2) ◽  
pp. 504-507
Author(s):  
G. W. Drake
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Average Molecular Weight ◽  
Weight Fraction ◽  
Considerable Proportion ◽  
Prolonged Storage ◽  
High Molecular Weight Fraction ◽  
The United Kingdom ◽  
Molecular Weight Fractions ◽  
Temperate Climates

Abstract Fractionation of the rubber hydrocarbon in temperate climates has usually resulted in high molecular-weight fractions, with a molecular weight of the order of one million. Bloomfield has shown that fresh latex contains a considerable proportion of hydrocarbon having an intrinsic viscosity (η) of 10 or over and, therefore, a molecular weight of well over 106. The fractionation technique used by Bloomfield in Malaya has now been applied by the writer to smoked sheet and to F rubber, working in the United Kingdom. No very high molecular-weight fractions were found in the smoked sheet, but the F rubber yielded a fraction of (η)=7.3 and a number average molecular weight 6×106, determined osmometrically. The average molecular weight of natural rubber when freshly prepared is probably well over a million, and includes a substantial portion having a molecular weight of several millions. By the time smoked sheet has reached temperate climates, the high molecular-weight portion has probably been converted to gel. F rubber, presumably because of its different method of preparation, retains the major part of its high molecular-weight material during prolonged storage.

Isoprene and Rubber. Part 29. High Molecular Hydrorubbers

1932 ◽  
Vol 5 (2) ◽  
pp. 136-140
Author(s):  
H. Staudinger ◽  
W. Feisst
Keyword(s):  
Molecular Weight ◽  
Catalytic Reduction ◽  
Molecular Form ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Rubber Part ◽  
Derivatives Of ◽  
Suitable Process

Abstract The molecular concept in organic chemistry is based upon the fact that the molecules, whose existence is proved by vapor density determinations, enter into chemical reactions as the smallest particles. If now it is assumed that organic molecular colloids like rubber are dissolved in dilute solution in molecular form then it must be proved that in the chemical transposition of macromolecules as well no change in the size of the macromolecules occurs. In the case of hemicolloids, therefore for molecular colloids with an average molecular weight of 1000 to 10,000, this has been proved by the reduction of polyindenes, especially of polysterenes, to hydroproducts with the same average molecular weight, and also by the fact that cyclorubbers do not change their molecular weight upon autoöxidation. The molecular weights of hemi-colloidal hydrocarbons are therefore invariable. This is much more difficult to prove in the case of rubber, although there are many more ways in which unsaturated rubber can be transposed than the stable polysterenes, polyindenes, and poly cyclorubbers. In most of the reactions with rubber, as in its action with nitrosobenzene, oxidizing agents, hydrogen halides, and halogens, an extensive decomposition takes place as a result of the instability of the molecule, which is referred to in another work. Therefore derivatives of rubber are not formed, but derivatives of hemi-colloidal decomposition products. The catalytic reduction of rubber in the cold appears to be the most suitable process of making it react without changing its molecular size in order to prove that in a chemical transposition its molecular weight remains the same.

Isoprene and Rubber. XIX. The Molecular Size of Rubber and Balata

1930 ◽  
Vol 3 (3) ◽  
pp. 519-521 ◽  
Author(s):  
H. Staudinger ◽  
H. F. Bondy
Keyword(s):  
Molecular Weight ◽  
Organic Solvent ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Dilute Solution ◽  
Decomposition Products ◽  
Viscosity Measurements ◽  
Gutta Percha ◽  
Preceding Work

Abstract It was shown in the preceding work that a very dilute solution of balata in an organic solvent contains macromolecules in solution and not micelles. The same is true of rubber. On the basis of these findings it is possible to calculate the molecular weight of rubber and balata from viscosity measurements by means of the formula developed in a previous work: M=η8p/c. Km. The supposition is made that the molecules of rubber and balata have the form of threads and double threads, respectively. Also it is necessary to determine the constant KKm, and this may be calculated in the case of low molecular products, where the average molecular weight can be determined as well as the viscosity of the solutions. Such semi-colloidal decomposition products were obtained by heating rubber or gutta-percha in either tetralin or xylene. As shown by the following table the four samples thus obtained gave the constant: 0.3×10−3,5

scholarly journals Effect of molecular size of 125I-labelled poly(vinylpyrrolidone) on its pinocytosis by rat visceral yolk sacs and rat peritoneal macrophages

1981 ◽  
Vol 196 (1) ◽  
pp. 49-55 ◽  
Author(s):  
R Duncan ◽  
M K Pratten ◽  
H C Cable ◽  
H Ringsdorf ◽  
J B Lloyd
Keyword(s):  
Molecular Weight ◽  
Molecular Size ◽  
Weight Fraction ◽  
Cell Types ◽  
Peritoneal Macrophages ◽  
Yolk Sac ◽  
High Molecular Weight Fraction ◽  
Molecular Weights ◽  
Molecular Weight Distributions

Rates of pinocytosis of different molecular-weight distributions of 125I-labelled poly(vinylpyrrolidone) by rat visceral yolk sacs and rat peritoneal macrophages were measured in vitro. Four preparations of mean molecular weights 50 000, 84 000, 700 000 and 7 000 000, were used. Macrophages captured the highest-molecular-weight preparation more rapidly than the other preparations. In contrast, rate of capture by the yolk sac decreased with increasing molecular weight. Incubations with a very-high-molecular-weight fraction derived from the 7 000 000-average-mol. wt. preparation clearly demonstrated that very large polymer molecules are not accumulated by the yolk sac, but are preferentially captured by macrophages. Analysis of the 125I-labelled poly(vinylpyrrolidone) internalized by the two cell types confirmed that low-molecular-weight material is preferred by the yolk sac, whereas the macrophage is less discriminating.

scholarly journals Cloud Condensation Nuclei properties of model and atmospheric HULIS

2006 ◽  
Vol 6 (9) ◽  
pp. 2465-2482 ◽  
Author(s):  
E. Dinar ◽  
I. Taraniuk ◽  
E. R. Graber ◽  
S. Katsman ◽  
T. Moise ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Fulvic Acid ◽  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Average Molecular Weight ◽  
Water Soluble ◽  
Cloud Droplets ◽  
Secondary Sources ◽  
Multifunctional Compounds ◽  
Physico Chemical

Abstract. Humic like substances (HULIS) have been identified as a major fraction of the organic component of atmospheric aerosols. These large multifunctional compounds of both primary and secondary sources are surface active and water soluble. Hence, it is expected that they could affect activation of organic aerosols into cloud droplets. We have compared the activation of aerosols containing atmospheric HULIS extracted from fresh, aged and pollution particles to activation of size fractionated fulvic acid from an aquatic source (Suwannee River Fulvic Acid), and correlated it to the estimated molecular weight and measured surface tension. A correlation was found between CCN-activation diameter of SRFA fractions and number average molecular weight of the fraction. The lower molecular weight fractions activated at lower critical diameters, which is explained by the greater number of solute species in the droplet with decreasing molecular weight. The three aerosol-extracted HULIS samples activated at lower diameters than any of the size-fractionated or bulk SRFA. The Köhler model was found to account for activation diameters, provided that accurate physico-chemical parameters are known.

scholarly journals Ultrasound-Assisted Ultra-Mild-Acid Hydrolisis of -Carrageenan

REAKTOR ◽  
2018 ◽  
Vol 17 (4) ◽  
pp. 191
Author(s):  
Ratnawati Ratnawati ◽  
Nita Indriyani
Keyword(s):  
Molecular Weight ◽  
Acid Hydrolysis ◽  
Average Molecular Weight ◽  
Weight Fraction ◽  
Number Average Molecular Weight ◽  
Hydrolysis Process ◽  
Higher Temperature ◽  
Ultrasound Assisted ◽  
Hydrolysis Of ◽  
Mild Acid

The low molecular weight fraction of κ-carrageenan is useful in biomedical applications. An ultrasound-assisted acid hydrolysis of κ-carrageenan has been studied. κ-carrageenan with an initial number-average molecular weight of 629 kDa was dispersed in distilled water to form a 5 g/l solution. The pH (3 and 6) of the solution was adjusted by adding HCl solution. The depolymerization reaction was carried out in an ultrasonic device at various temperatures (30, 40, 50, and 60°C) and times (8, 16, 24, and 32 min). The experimental results showed that ultrasound positively contributed to acid hydrolysis process. The number-average molecular weight of the treated k-carrageenan was lower or the percentage of reduction was higher at lower pH, longer reaction time, and higher temperature. The lowest number-average molecular weight (14 kDa) or the highest percent of molecular weight reduction reduction (97.7%) was achieved after ultrasonic irradiation at 60°C and pH 3 for 32 min. Keywords: depolymerization; midpoint scission; ultrasonication

Scale-free power-law distribution of nonlinear polymers formed in a homeostatic system

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Hidetaka Tobita
Keyword(s):  
Molecular Weight ◽  
Power Law ◽  
Average Molecular Weight ◽  
Weight Fraction ◽  
B Value ◽  
Power Law Distribution ◽  
Scale Free ◽  
Fraction Distribution ◽  
Continuously Stirred Tank Reactor ◽  
Simple Stochastic Model

Abstract A power-law distribution of molecular weight is found for low-density polyethylene formed in a one-zone autoclave reactor. This reactor could be modelled as a continuously stirred tank reactor (CSTR) operated under homeostatic conditions where the concentration of each component as well as temperature and pressure are kept constant. A simple stochastic model is used to investigate the molecular weight distribution (MWD) formed in free-radical polymerization involving chain transfer to polymer. The MWD profiles are dominated by the Pb value, which represents the probability that the chain end is connected to a backbone chain. By increasing Pb, MWD changes from an exponential to a powerlaw distribution. A scale-free power-law distribution is found for Pb > 0.5. Because the power of the weight fraction distribution, W(M) ~ M -γ, is 1 < γ < 2, the number average molecular weight will reach a stationary-state value but the weightaverage may continue to increase unlimitedly under ideal CSTR conditions.

Chromatography of heparin on Sepharose–lysine: molecular size fractionation and its relevance to thrombin and antithrombin III binding

1979 ◽  
Vol 57 (10) ◽  
pp. 1183-1190 ◽  
Author(s):  
M. W. C. Hatton ◽  
L. R. Berry ◽  
H. Kaur ◽  
A. Koj ◽  
E. Regoeczi
Keyword(s):  
Molecular Weight ◽  
Antithrombin Iii ◽  
Binding Capacity ◽  
Anticoagulant Activity ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Lysine Content ◽  
Heparin Binding ◽  
Significant Difference ◽  
Lysine Residues

Batches of Sepharose–lysine, which varied in lysine content from 35 to 430 μmol/g of dry gel, were prepared by varying the quantity of CNBr in the activation reaction. The batches were tested for heparin binding by using a controlled chromatographic procedure. Sepharose–lysine, containing < 150 μmol of lysine/g, did not significantly bind heparin whereas conjugates with > 400 μmol/g retained the entire heparin load. For intermediate batches of Sepharose–lysine (150–400 μmol/g) the quantity of heparin bound largely paralleled the lysine content. Thus, Sepharose–lysine of an intermediate lysine content separated heparin into an unretained fraction and a bound fraction which was recovered from the column by eluting with 1 M NaCl. On testing for anticoagulant activity by factor Xa inhibition assay, no significant difference in specific anticoagulant activity was observed between these heparin fractions and the heparin load. However, from gel filtration studies, a substantial difference in molecular size was noted. An unretained heparin fraction from Sepharose–lysine was of a lower average molecular weight than the parent heparin. In contrast, a retained heparin peak was of a higher average molecular weight compared with the parent heparin. These observations were confirmed by studying the chromatographic properties of low (10 000) and high (23 000) molecular weight heparin samples on various Sepharose–lysine batches. A model is proposed to explain this discriminating property of Sepharose–lysine. For a conjugate containing 400 μmol/g, the mean lysine spacing is calculated at 47 Å (1 Å = 0.1 nm), which is approximately equivalent to five to six disaccharide units in heparin.The property of Sepharose–lysine to bind heparin was compared with the affinities of the mucopolysaccharide for both thrombin and antithrombin III. Evidence has been proposed for the involvement of lysine residues of antithrombin III in this process. Our investigations suggest that lysine, in addition to arginine, groups of thrombin are also involved in heparin binding. By specifically modifying two to four lysine residues using nitrous acid, the heparin-binding capacity of the enzyme and its plasma clotting activity were largely destroyed, although the esterase activity was retained.

THE NUMBER-AVERAGE AND WEIGHT-AVERAGE MOLECULAR WEIGHT OF SOME NONIONIC SURFACE-ACTIVE AGENTS

1962 ◽  
Vol 40 (5) ◽  
pp. 957-962 ◽  
Author(s):  
A. F. Sirianni ◽  
J. M. G. Cowie ◽  
I. E. Puddington
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
Benzene Solution ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Surface Active Agents ◽  
Pressure Lowering ◽  
Surface Active ◽  
Active Substances

Further evidence for the existence of large differences between the weight- and number-average molecular weight for nonionic surface-active substances in nonaqueous solvents has been found when the property is assessed by light-scattering and vapor-pressure-lowering measurements. Equilibrium ultracentrifuge measurements support the results obtained by vapor-pressure-lowering determinations. Sorbitan and glycerol monostearates have been examined in benzene solution.

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