Isoprene and Rubber. Part 33. End Groups in Rubber

1932 ◽  
Vol 5 (3) ◽  
pp. 263-264
Author(s):  
H. Staudinger
Keyword(s):  
Molecular Weight ◽  
Recent Work ◽  
Average Length ◽  
The Other ◽  
Ozone Decomposition ◽  
Other Hand ◽  
End Groups ◽  
Rubber Part ◽  
End Members ◽  
Foreign Impurities

Abstract In a recent work, Pummerer, Ebermeyer, and Gerlach attempted to identify end members in the rubber molecule by ozone decomposition, and in this way to determine the molecular weight of rubber by chemical means. In this connection they say: The basis for the validity of the conclusions derived from the cleavage fragments on the average length of the rubber chain is that this hydrocarbon contains no structurally foreign impurities, but is built up of homogeneous molecules, though of perhaps different lengths. Pummerer abandons his earlier view, according to which rubber is composed of a uniform base molecule, in favor of concepts held by me for years on the constitution of rubber and other high polymeric substances. As was first proved for synthetic products and as shown for balata and rubber, these substances consist of a mixture of similarly constituted molecules of various lengths and therefore of a mixture of homologous polymers. Pummerer has now adopted this concept, but on the other hand he does not agree on the question of the molecular weight.

Effect on Polymer Chain Structure Caused by the Molar Fraction of 4-Hydroxybutyrate in Poly(3-hydroxybutyrate- co -4-hydroxybutyrate)

2012 ◽  
Vol 602-604 ◽  
pp. 776-780
Author(s):  
Zhi Qiang Li ◽  
Mei Li ◽  
Wei Jia Fan
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Polymer Chain ◽  
Molar Fraction ◽  
Chain Structure ◽  
The Other ◽  
Mean Square ◽  
Polarizing Microscope ◽  
Other Hand ◽  
The Mean

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)copolymer [P(3HB-co-4HB)] is a kind of biodegradable high molecular polymer produced by bioaccumulation. Because of the good biodegradability and biocompatibility, P(3HB-co-4HB)s have attracted wide attention . At first, the intrinsic viscosity[η] in good solvent of P(3HB-co-4HB) s with varying contents of 4HB was investigated in different temperature. Second, observed the changes of crystallization gathered state caused by the varying contents of 4HB by polarizing microscope. The results show that to the P(3HB-co-4HB)s in same molecular weight, the intrinsic viscosity[η] in good solvent barely changes when the mole fractions of 4HB increase. On the other hand, the mean square end to end distances[0] of macromolecular flexible chains increase with the mole fractions of 4HB. At the same time, the states of aggregation change from spherulites to dendrites. In this investigation, we discuss the reasons of the differences in depth.

Faith and Goodness

1989 ◽  
Vol 25 ◽  
pp. 167-191
Author(s):  
Eleonore Stump
Keyword(s):  
Recent Work ◽  
Religious Belief ◽  
The Other ◽  
Alvin Plantinga ◽  
Belief In God ◽  
Other Hand ◽  
The Subject ◽  
Richard Swinburne ◽  
The Relationship

Recent work on the subject of faith has tended to focus on the epistemology of religious belief, considering such issues as whether beliefs held in faith are rational and how they may be justified. Richard Swinburne, for example, has developed an intricate explanation of the relationship between the propositions of faith and the evidence for them. Alvin Plantinga, on the other hand, has maintained that belief in God may be properly basic, that is, that a belief that God exists can be part of the foundation of a rational noetic structure. This sort of work has been useful in drawing attention to significant issues in the epistemology of religion, but these approaches to faith seem to me also to deepen some long-standing perplexities about traditional Christian views of faith.

IV.—On some Freshwater Mollusca from the Pliocene Deposits of East Anglia

1911 ◽  
Vol 8 (9) ◽  
pp. 401-403 ◽  
Author(s):  
A. S. Kennard ◽  
B. B. Woodward
Keyword(s):  
New Species ◽  
Recent Work ◽  
The Other ◽  
East Anglia ◽  
Other Hand ◽  
Differences Of Opinion ◽  
Correct Determination

Non-marine Mollusca are extremely rare in the Pliocene deposits of this country, which fact must always be a matter of regret to the Palæontologist, since they are of the utmost importance in connexion with the origin of our present fauna. Unfortunately, in addition to their rarity, they are often decorticated or fragmentary, whence no doubt the differences in opinion as to their correct determination. A re-examination of all the available material has convinced us that there is still much to be done before it will be possible to reach finality. In these matters so much depends on one's standpoint. If one starts with the preconceived idea that the Pliocene shells must be identical with the recent forms, it is easy enough to identify them, even if one has to go to Japan or Greenland to find its present habitat. If, on the other hand, one considers it better to study carefully the results of recent work on other branches of the fauna, it is obvious that different results will be arrived at. Hence we are quite prepared for any differences of opinion as to the correctness of our views or the wisdom of creating four new species, as we now venture to do.

The false dichotomy of imagery

2002 ◽  
Vol 25 (2) ◽  
pp. 211-211 ◽  
Author(s):  
Nigel J. T. Thomas
Keyword(s):  
Activity Theory ◽  
Recent Work ◽  
The Other ◽  
Active Perception ◽  
Popular Belief ◽  
Other Hand ◽  
Description Theory ◽  
False Dichotomy

Pylyshyn's critique is powerful. Pictorial theories of imagery fail. On the other hand, the symbolic description theory he manifestly still favors also fails, lacking the semantic foundation necessary to ground imagery's intentionality and consciousness. However, contrary to popular belief, these two theory types do not exhaust available options. Recent work on embodied, active perception supports the alternative perceptual activity theory of imagery.

scholarly journals The effect on the blood sugar of fish of various conditions including removal of the principal islets (isletectomy)

1925 ◽  
Vol 98 (687) ◽  
pp. 1-29 ◽  
Keyword(s):  
Recent Work ◽  
Blood Sugar ◽  
Islets Of Langerhans ◽  
Pancreatic Tissue ◽  
The Other ◽  
Gradual Decline ◽  
Other Hand ◽  
Bony Fishes

In fishes the sugar of the blood and the glycogen of the liver have been found to vary considerably even in individuals of the same species, and still more so in those of different species. Practically nothing is known definitely of the causes for these variations, and this we consider an important problem to investigate, especially since light might thereby be thrown on the nature of the metabolism of carbohydrates in cold-blooded animals in which the intermediary stages proceed more slowly than in warm-blooded animals. Our interest was aroused in the behaviour of the blood sugar of fishes for other reasons as well. In certain of the bony fishes (Teleostei) the islets of Langerhans exist as definite glands which have come to be known as the “principal islets.” Being more or less separated from the pancreatic tissue itself, these can readily be excised, thus making it possible, by examination of the blood sugar, to determine whether a diabetic condition can be induced by isletectomy without removal of any of the pancreas proper. It was of interest also to see whether insulin can affect the blood sugar. Before such investigations could be undertaken it was necessary to know exactly the degree to which the blood sugar of different fishes of the same species may vary independently of such an operation. Lang and Macleod (1), in confirmation of earlier work by Diamare (2) and of Bierry and Fandard (3), found that there are usually only traces of sugar in the blood of the Elasmobranchi, such as Squalus (dog-fish), but that considerable amounts may occur in the blood of representative Teleostei, such as Cyprinus (carp). In the latter fish it was also noted that the amounts may vary from 0·058 to 0·300 per cent. Fandard and Ranc (4) have stated that the blood sugar in fishes is peculiarly susceptible to asphyxial conditions, but so far as we have been able to find they have published no details of their observations. The most important recent work is that of E. L. Scott (5), who has observed the blood sugar in Mustelis canis , the fish prior to the observations being kept in traps which were exposed to tide water and, during them, in shallow tanks. The percentage of oxygen was also frequently determined in the water of the tanks. It was found that no blood sugar, or only traces, could be detected in six out of eight individuals, which are described as having been in a subnormal condition. On the other hand, when the fish were asphyxiated by keeping them out of water for varying periods of time, the blood sugar rose rapidly, to attain, in two specimens, a maximum of about 0·240 per cent, after four minutes, followed by a gradual decline, so that a level of 0·032 was reached in one specimen after 15 minutes. The degree of variability in the results is, however, very great, and they do not seem to us to justify the conclusion that the sugar rises within a few minutes and then falls again during the asphyxial period.

scholarly journals THE MOLECULAR WEIGHT OF ANTIBODIES

1937 ◽  
Vol 65 (3) ◽  
pp. 393-414 ◽  
Author(s):  
Michael Heidelberger ◽  
Kai O. Pedersen
Keyword(s):  
Molecular Weight ◽  
Molecular Species ◽  
Principal Component ◽  
The Other ◽  
Type I ◽  
Egg Albumin ◽  
Type Iii ◽  
Sedimentation Constant ◽  
Other Hand ◽  
Immune Rabbit

1. Highly purified rabbit Type III pneumococcus anticarbohydrate proved to be homogeneous in the ultracentrifuge and its sedimentation constant, 7.0·10–13, did not differ from that of the principal component of normal rabbit globulin or of immune rabbit globulin containing up to 50 per cent of anti-egg albumin. The molecular weight of antibody in the rabbit is therefore probably very close to that of the principal normal globulin component, namely, 150,000. 2. Highly purified horse Type I pneumococcus anticarbohydrate, on the other hand, was only homogeneous in the ultracentrifuge when prepared from sera stored without preservative. Its sedimentation constant, 18.4·10–13, coincided with that of the principal globulin component in most of the Felton solutions and purified antibody solutions studied. The molecular weight of pneumococcus anticarbohydrate in the horse is probably three to four times that of the principal normal globulin component. 3. The significance of the differences between pneumococcus anticarbohydrate formed in the rabbit and in the horse is discussed. 4. Results are given of ultracentrifuge studies on the molecular species in solutions of egg albumin-anti-egg albumin specific precipitates dissolved in excess egg albumin. The implications of the results are discussed.

scholarly journals Von Willebrand factor: structure, properties and role in the process of hemostasis

2020 ◽  
pp. 3-13
Author(s):  
N Shurko ◽  
Keyword(s):  
Molecular Weight ◽  
Von Willebrand Factor ◽  
Functional Ability ◽  
Platelet Adhesion ◽  
The Other ◽  
Hemostasis System ◽  
Other Hand ◽  
Thrombotic Complications ◽  
Von Willebrand ◽  
Willebrand Factor

The article reviews the scientific papars on the structure, function and biological role of von Willebrand factor (vWF). The vWF mainly was considered as the main factor in the development of bleeding disorders (von Willebrand’s disease). On the other hand, it can be able the cause thrombotic complications through to the functional ability of the factor to stimulate platelet adhesion. The aim of this work was to conduct an analysis of the structure of the factor, its role in the process of hemostasis to determine a border between two opposing processes. Von Willebrand factor is a hemostatic, multimeric glycoprotein, one of the key components of the hemostasis system, taking an active part at startup mechanisms of platelet adhesion at the site of vesselendothelial damage. On the other hand, another important function of vWF is co-factor activity related to coagulation factor VIII (FVIII), which is to stabilize its activity, promoting thrombin activation and preventing the cleavage of the molecule by blood plasma proteinases. The human gene of vWF is localized on the short arm of the 12 chromosome, contains 52 exons and covers approximately 180 kb. VWF is made by endothelial cells and by bone marrow megakaryocytes. The factor is preserved in the Weibel-Palade bodies of endotolial cells and α-granules of platelets. The primary pro-polypeptide consists of 2813 amino acid, of which 2050 form the mature peptide. The molecular weight of vWF is 220 kDa. In bloodstreamv WF circulates as a multimeric protein with a molecular weight from 400 to 20,000 kDa. The synthesized molecule has the next domain structure: D1-D2-D’-D3-A1-A2-A3-D4-C1-C2-C3-C4-C5-C6-CK. Domains are responsible for binding various proteins, including FVIII, fibrin, collagen, heparin, complement components etcetra. Von Willebrand disease (vWD) is the most common autosomal inherited disorder of the hemostasis system (from 0.6 to 2.0% of the population) and the cause is a genetic deficiency of quantitative and/or qualitative abnormal multimeric structure of the vWF molecule. There are three main subtypes of vWD. Quite often in such patients there is a decrease in FVIII activity, as an indirect consequence of changes in vWF. The basic principle of vWD treatment is based on the normalization of vWF and/or FVIII levels by increasing the level of external vWF under the action of desmopressin or the introduction of factor concentrates. In contrast to hereditary vWD, acquired von Willebrand syndrome is a relatively rare acquired bleeding of the blood coagulation system (incidence from 0.04 to 0.13 %) associated with various underlying diseases. For today a significant amount of research devoted to the relationship between vWF and thrombotic complications, that is due functional ability of the factor stimulate platelet adhesion. In particular, there are reports of the following complications in: pneumonia caused by Streptococcus pneumoniae; COVID-19; polycythemia vera; chronic kidney disease etcetra.

Railroads and Regulation, 1877–1916: Conspiracy or Public Interest?

1967 ◽  
Vol 27 (2) ◽  
pp. 230-242 ◽  
Author(s):  
Robert W. Harbeson
Keyword(s):  
Recent Work ◽  
Public Interest ◽  
State Regulation ◽  
The Other ◽  
Strict Sense ◽  
Federal Regulation ◽  
Other Hand ◽  
Railroad System

Professor Gabriel Kolko in his recent work, Railroads and Regulation, 1877–1916, presents an interpretation or the origin, motivation, and consequences of the movement for federal regulation of railroads which differs in important respects from that which has hitherto been generally accepted. Thus it has generally been held that railway regulation was a response to the demands of farmers and other shippers for protection against monopolistic and discriminatory tactics on the part of the railroads and that regulation was bitterly resisted by the latter. Kolko, on the other hand, holds that regulation was actually welcomed by the railroads as a means of securing the rate and profit stability which they were unable to maintain by their own action, and that “the railroads, not the farmers and shippers, were the most important single advocates of federal regulation from 1877 to 1916” (p. 3). He concedes that “the movement for federal regulation of the railroad system was not, in any strict sense, deliberately initiated by the railroads’ (p. 20) and that legislation could not have been passed without shipper support, but points out that shippers were either inarticulate or divided with respect to the kind of regulation, if any, desired, and that the railroads were always able to secure the support of enough shipper groups to insure passage of the legislation which they favored. Furthermore, the railroads welcomed federal as opposed to state regulation, since they regarded the latter as punitive and restrictive and less amenable to their influence than federal regulation.

Monodispersepoly[BMA-co-(COPS-I)] Particles by Soap-Free Emulsion Copolymerization and Its Optical Properties as Photonic Crystals

2015 ◽  
Vol 15 (10) ◽  
pp. 7671-7678
Author(s):  
Ki Chang Lee ◽  
Hun Seung Choo
Keyword(s):  
Molecular Weight ◽  
Optical Properties ◽  
Zeta Potential ◽  
Photonic Crystals ◽  
The Other ◽  
Refractive Indices ◽  
Emulsion Copolymerization ◽  
Colloidal Photonic Crystals ◽  
Other Hand ◽  
Number Of Particles

In order to study the surfactant-free emulsion copolymerization of benzyl methacrylate (BMA) with sodium 1-allyloxy-2-hydroxypropane sulfonate (COPS-I) and the resulting optical properties, a series of experiments was carried out at various reaction conditions such as the changes of BMA concentration, COPS-I concentration, BMA concentration under a fixed COPS-I amount, initiator and divinyl benzene (DVB) concentration. All the latices showed highly monodispersed spherical particles in the size range of 144∼435 nm and the respective shiny structural colors from their colloidal photonic crystals. It is found that the changes in such polymerization factors greatly affect the number of particles and particle diameter, polymerization rate, molecular weight, zeta-potential, and refractive indices. The increase of number of particles led to the increased rate of polymerization and zeta-potential of the latices, on the other hand, to the decreased molecular weight. Refractive indices and the reflectivity increased with COPS-I concentration, on the other hand, and decreased with DVB concentration. Especially, refractive indices of the resulting poly[BMA-co-(COPS-I)] colloidal photonic crystals showed much higher values of 1.65∼2.21 than that of polystyrene, due to the formation of core–shell shaped morphology. Monodisperse and high refractive index of poly[BMA-co-(COPS-I)] particles prepared in this work could be used for the study in photonic crystals and electrophoretic display.

Behavior of Different Fractions of Purified Hevea Rubber during Vulcanization

1949 ◽  
Vol 22 (4) ◽  
pp. 994-999
Author(s):  
G. T. Verghese
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
The Other ◽  
Stress Strain ◽  
Strain Behavior ◽  
Other Hand ◽  
The Difference

Abstract Considerable data on the vulcanization characteristics of molecular fractions of ordinary (unpurified) natural rubber are available. There is, on the other hand, little information of any systematic work on the vulcanization of purified rubber and of its fractions. Pummerer and Pahl vulcanized the sol and gel fractions obtained from purified Hevea rubber, and also the purified whole rubber. But apart from a statement that whole rubber vulcanized much faster than the two fractions obtained from it, no details have been published. Vulcanization of purified whole rubber and of its sol and gel fractions was studied also by Smith and Holt. They concluded that the difference which they observed in the stress-strain behavior of the fractions and whole rubber was due to differences in the rubber which persisted through vulcanization. The present paper deals with a study of the vulcanization characteristics of different fractions of purified rubber prepared by a method described in a previous paper. Also, for comparative purposes a similar study was made of the corresponding fractions of unpurified rubber. As the difference in molecular weight of some of the fractions obtained by the above method was rather small, a grouping of the fractions was made as follows :

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