The Surface Tension of Rubber Solutions

1931 ◽  
Vol 4 (3) ◽  
pp. 354-360
Author(s):  
G. W. Shacklock
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Surface Tension ◽  
Benzene Solution ◽  
Rubber Particle ◽  
Mechanical Action ◽  
The Past ◽  
Pure Product ◽  
Simple Molecules ◽  
Improved Methods

Abstract During the past few years much attention has been paid to the constitution of raw rubber. The much improved methods of production of plantation rubber have resulted in a reasonably pure product available for investigation, and chemical analysis undoubtedly shows an empirical formula of C5H8 for the hydrocarbon. From this point onward, knowledge becomes less certain. Osmotic pressure and molecular weight measurements give no confirmation of a simple molecular structure, but show, in benzene solution, a behavior comparable with that of colloids. This is supported by experiments on swelling and viscosity, and by ultramicroscopic examination, all of which lead to the conclusion that rubber is a lyophilic colloid. Hence arose the concept that the rubber particle is a polymer of simple molecules of formula C5H8 (possibly isoprene), such a structure being in agreement with the production of rubber-like substances by the action of sodium upon isoprene and butadiene (Harries, Annalen, 395, 211 (1912)). The decrease in viscosity of a rubber solution with increasing periods of mastication of the rubber is hence regarded as a measure of depolymerization due to mechanical action; the increased ease of solution after mastication is confirmatory evidence.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

On the assembly and structural modulation of lens fiber junctions

1984 ◽  
Vol 42 ◽  
pp. 110-113
Author(s):  
E.L. Benedetti ◽  
I. Dunia ◽  
Do Ngoc Lien ◽  
O. Vallon ◽  
D. Louvard ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Natural History ◽  
Intercellular Junctions ◽  
Eye Lens ◽  
Membrane Domains ◽  
Functional Polymorphism ◽  
Lens Fiber ◽  
The Past ◽  
Structural Modulation ◽  
Biochemical Difference

In the eye lens emerging molecular and structural patterns apparently cohabit with the remnants of the past. The lens in a rather puzzling fashion sums up its own natural history and even transient steps of the differentiation are memorized. A prototype of this situation is well outlined by the study of the lenticular intercellular junctions. These membrane domains exhibit structural, biochemical and perhaps functional polymorphism reflecting throughout life the multiple steps of the differentiation of the epithelium into fibers and of the ageing process of the lenticular cells.The most striking biochemical difference between the membrane derived from the epithelium and from the fibers respectively, concerns the presence of the 26,000 molecular weight polypeptide (MP26) in the latter membranes.

ANALISA KANDUNGAN BETA-GLUKAN LARUT AIR DAN LARUT ALKALI DARI TUBUH BUAH JAMUR TIRAM (Pleurotus ostreatus) DAN SHIITAKE (Lentinus edodes)

2013 ◽  
Vol 13 (3) ◽  
Author(s):  
Netty Widyastuti ◽  
Teguh Baruji ◽  
Henky Isnawan ◽  
Priyo Wahyudi ◽  
Donowati Donowati
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Immune System ◽  
Pleurotus Ostreatus ◽  
Water Soluble ◽  
Low Molecular Weight ◽  
Lentinus Edodes ◽  
Beta Glucan ◽  
Oyster Mushrooms ◽  
The Difference

Beta glucan is a polysaccharide compound, generally not soluble inwater and resistant to acid. Beta glucan is used as an immunomodulator (enhancing the immune system) in mammals is usually a beta-glucan soluble in water, easily absorbed and has a low molecular weight. Several example of beta-glucan such as cellulose (β-1 ,4-glucan), lentinan (β-1 0.6-glucan) and (β-1 ,3-glucan), pleuran (β-1, 6 and β-1 ,3-glucan) are isolated from species of fungi Basidiomycota include mushrooms (Pleurotus ostreatus) and shiitake (Lentinus edodes).The purpose of thisresearch activity is to obtain beta-glucan compound that can be dissolved in water and in alkali derived from fungi Basidiomycota, i.e, Oyster mushrooms (Pleurotus ostreatus) and shiitake (Lentinus edodes). The result of beta-glucan compared to characterize the resulting beta glucan that is molecular structure . The difference of beta glucan extraction is based on the differences in solubility of beta-glucan. Beta glucan could be water soluble and insoluble water.

scholarly journals Heterogeneity of SARS-CoV-2 virus produced in cell culture revealed by shotgun proteomics and supported by genome sequencing

2021 ◽  
Author(s):  
Fabrice Gallais ◽  
Olivier Pible ◽  
Jean-Charles Gaillard ◽  
Stéphanie Debroas ◽  
Hélène Batina ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Cell Culture ◽  
Shotgun Proteomics ◽  
Rapid Analysis ◽  
Diagnostic Tools ◽  
Tandem Mass ◽  
The Past ◽  
Viral Particles ◽  
Depth Analysis ◽  
The Subject

AbstractCOVID-19 is the most disturbing pandemic of the past hundred years. Its causative agent, the SARS-CoV-2 virus, has been the subject of an unprecedented investigation to characterize its molecular structure and intimate functioning. While markers for its detection have been proposed and several diagnostic methodologies developed, its propensity to evolve and evade diagnostic tools and the immune response is of great concern. The recent spread of new variants with increased infectivity requires even more attention. Here, we document how shotgun proteomics can be useful for rapidly monitoring the evolution of the SARS-CoV-2 virus. We evaluated the heterogeneity of purified SARS-CoV-2 virus obtained after culturing in the Vero E6 cell line. We found that cell culture induces significant changes that are translated at the protein level, such changes being detectable by tandem mass spectrometry. Production of viral particles requires careful quality control which can be easily performed by shotgun proteomics. Although considered relatively stable so far, the SARS-CoV-2 genome turns out to be prone to frequent variations. Therefore, the sequencing of SARS-CoV-2 variants from patients reporting only the consensus genome after its amplification would deserve more attention and could benefit from more in-depth analysis of low level but crystal-clear signals, as well as complementary and rapid analysis by shotgun proteomics. Graphical abstract

Explosive Removal of Concrete From Reinforced Walls

2007 ◽  
Author(s):  
Denis D. Rickman ◽  
John Q. Ehrgott ◽  
Stephen A. Akers ◽  
Jon E. Windham ◽  
Dennis W. Moore
Keyword(s):  
Explosive Charge ◽  
Research Effort ◽  
Us Army ◽  
Steel Reinforced Concrete ◽  
The Past ◽  
The Us ◽  
Development Center ◽  
The Relationship ◽  
Improved Methods ◽  
Combat Environment

During the past several years, the US Army has focused considerable attention toward developing improved methods for breaching walls in the urban combat environment. A major thrust area is centered on finding improved methods to breach the toughest wall type that Army units are likely to face: a double (steel) reinforced concrete (RC) wall. One impediment to this effort is that the relationship between the contact explosive charge configuration and the quantity of concrete removed has not been thoroughly understood. The U.S. Army Engineer Research and Development Center has conducted a research effort to better define the effectiveness of various explosive charge configurations in breaching RC walls. This paper presents a discussion of results from this research.

Sorption of GR-S Type of Polymer on Carbon Black. III. Sorption by Commercial Blacks

1953 ◽  
Vol 26 (1) ◽  
pp. 102-114 ◽  
Author(s):  
I. M. Kolthoff ◽  
R. G. Gutmacher
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Intrinsic Viscosity ◽  
Benzene Solution ◽  
Weight Fraction ◽  
High Molecular Weight Fraction ◽  
Molecular Weights ◽  
Bound Rubber ◽  
Flow Through ◽  
Peculiar Behavior

Abstract The sorption capacities toward GR-S five commercial carbon blacks are in decreasing order: Spheron-6, Vulcan-1, Philblack-0, Sterling-105, Philblack-A. Apparently, the sorption is not related to surface area. The sorption on Vulcan-1 of GR-S from its solutions in seven different solvents or mixtures of solvents increases with decreasing solvent power for the rubber. The sorption curves of two “cold rubbers,” polymerized at −10 and +5° respectively, showed little difference from that of 50° GR-S. Previous heating of carbon black in nitrogen at 500 or 1100° increased the sorption by about 20 per cent over unheated carbon. Air-heating of carbon black at 425° did not cause a difference in the sorption from benzene solution, but produced an increase in the sorption of rubber from n-heptane solution. In the range 75% butadiene-25% styrene to 5% butadiene-95% styrene, there is practically no effect of the degree of unsaturation on the sorption. Polystyrene of high intrinsic viscosity exhibits a peculiar behavior with furnace blacks. Vulcan-1 sorbed microgel as well as the sol fraction from n-heptane solutions of GR-S containing microgel (conversion 74.7 and 81.5 per cent). There was no appreciable difference in the amount of sorption of rubber fractions having average molecular weights varying from 433,000 to 85,000. There is little change in the amount sorbed after two hours of shaking, but the intrinsic viscosity of the residual rubber decreases with time. The low molecular-weight rubber is sorbed more rapidly, but is slowly replaced by the more tightly sorbed high molecular weight fraction. Partial fractionation of a rubber sample can be achieved by allowing the rubber solution to flow through a column of weakly sorbing carbon black. A large portion of the sorbed rubber can be recovered from the column by washing it with a good solvent such as xylene. Bound rubber is produced by intimate mixing of equal parts of carbon black and rubber swollen in chloroform, when the mixture is dried in vacuum at 80° or at room temperature. Milling is not essential to get bound rubber.

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 Twenty Years of Time Series Econometrics in Ten Pictures

2017 ◽  
Vol 31 (2) ◽  
pp. 59-86 ◽  
Author(s):  
James H. Stock ◽  
Mark W. Watson
Keyword(s):  
Time Series ◽  
Causal Effects ◽  
Economic Time Series ◽  
Economic Relationships ◽  
Time Series Econometrics ◽  
The Past ◽  
Dynamic Structural Models ◽  
Economic Time ◽  
Dynamic Stochastic ◽  
Improved Methods

This review tells the story of the past 20 years of time series econometrics through ten pictures. These pictures illustrate six broad areas of progress in time series econometrics: estimation of dynamic causal effects; estimation of dynamic structural models with optimizing agents (specifically, dynamic stochastic equilibrium models); methods for exploiting information in “big data” that are specialized to economic time series; improved methods for forecasting and for monitoring the economy; tools for modeling time variation in economic relationships; and improved methods for statistical inference. Taken together, the pictures show how 20 years of research have improved our ability to undertake our professional responsibilities. These pictures also remind us of the close connection between econometric theory and the empirical problems that motivate the theory, and of how the best econometric theory tends to arise from practical empirical problems.

A COMPARISON OF TOPICAL AND SUBCUTANEOUS METHODS OF ADMINISTRATION OF SIXTEEN OESTROGENS

1963 ◽  
Vol 26 (3) ◽  
pp. 317-329 ◽  
Author(s):  
C. F. MORGAN
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Melting Point ◽  
Uterine Weight ◽  
Rank Orders ◽  
Target Organs ◽  
Structure And Activity ◽  
Response Variables

SUMMARY This study showed that the application of hormones directly on the surface of the skin will result in uterine and vaginal weight stimulation, at times equal to and sometimes more effective than effects obtained by s.c. injection of the same hormones in the same concentration and over the same length of time. This effect was apparent, using sixteen different oestrogens. It was also shown that the uterine weight response is more sensitive and discriminatory in detecting differences between the potencies of oestrogens than is the vaginal weight response. The rank orders by both response variables, whether by topical or s.c. administration, were similar. It was shown statistically that the differences in potency of the sixteen oestrogens tested in this study are related more to certain molecular structure than to difference in solubility, molecular weight, or melting point. It was postulated that the potency of the oestrogens was related to their molecular structure and activity within the target organs.

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