bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of the proliferation of cocultured gonocytes and sertoli cells by retinoids, triiodothyronine, and intracellular signaling factors: Differences between fetal and neonatal cells
Authors: Boulogne Barbara , Habert René , Levacher Christine
Published: April 2003

The regulation of early fetal germ cell growth has not been studied in cell culture, probably due to the poor survival of these cells. However, cell culture is the only system in which the control of cell growth can be studied independently of the influence of secreted testicular factors, which are diluted in the medium. We successfully cultured dispersed testicular cells from 16.5‐day‐old rat fetuses in defined medium and compared the growth of these cells with that of cells from 3‐day‐old neonates. In this system, fetal gonocytes displayed low levels of mitotic activity and their numbers remained stable. In contrast, neonatal gonocytes displayed high levels of mitotic activity and increased in number, these characteristics resembling those observed in vivo. We found that retinoic acid had deleterious effects on the number of gonocytes but did not affect Sertoli cell proliferation in fetal and neonatal cell cultures. Moreover, in fetal cell cultures, the decrease in the number of gonocytes resulted from a decrease in mitotic activity, probably due to a direct effect of retinoids on fetal gonocytes. Among the selective agonists for the retinoic acid receptor (RARα agonist, RARβ agonist, and RARγ agonist) and the retinoic X receptor (pan‐RXR agonist) tested, only the RARα agonist reproduced the effects of retinoic acid at concentrations lower than its Kd value in both fetal and neonatal cell cultures. As both RARα and RXRα are present in fetal and neonatal gonocytes, we suggest that retinoic acid exerts its effects on gonocytes via a RARα‐RXRα heterodimer, with RARα functioning as an active partner and RXRα as a passive partner. In this culture system, we show for the first time that triiodothyronine (T3) inhibits testicular fetal Sertoli cell and germ cell growth. We also tested intracellular signaling factors and found that a cAMP analog increased Sertoli cell proliferation and germ cell survival in both fetal and neonatal cells whereas phorbol esters (PMA) strongly inhibited the proliferation of fetal but not of neonatal gonocytes. None of the tested factors (T3, dbcAMP, and PMA) seemed to interact with the all‐trans retinoic acid pathway. Thus, fetal gonocytes and neonatal gonocytes differ in intrinsic properties, and their growth is not regulated in the same manner. Despite their low level of mitotic activity, fetal gonocytes were more sensitive to various factors than neonatal gonocytes. Mol. Reprod. Dev. 65: 194–203, 2003. © 2003 Wiley‐Liss, Inc.
Conventional DTI vs. slow and fast diffusion tensors in cat visual cortex
Authors: Ronen Itamar , Kim Keun‐Ho , Garwood Michael , Ugurbil Kamil , Kim Dae‐Shik
Published: April 2003

Diffusion tensor imaging (DTI) uses water diffusion anisotropy in axonal fibers to provide a tool for analyzing and tracking those fibers in brain white matter. In the present work, multidirectional diffusion MRI data were collected from a cat brain and decomposed into slow and fast diffusion tensors and directly compared with conventional DTI data from the same imaging slice. The fractional anisotropy of the slow diffusing component (Dslow) was significantly higher than the anisotropy measured by conventional DTI while reflecting a similar directionality and appeared to account for most of the anisotropy observed in gray matter, where the fiber density is notoriously low. Preliminary results of fiber tracking based on the slow diffusion component are shown. Fibers generated based on the slow diffusion component appear to follow the vertical fibers in gray matter. DslowTI may provide a way for increasing the sensitivity to anisotropic structures in cortical gray matter. Magn Reson Med 49:785–790, 2003. © 2003 Wiley‐Liss, Inc.
Stereotaxic assembly and procedures for simultaneous electrophysiological and MRI study of conscious rat
Authors: Khubchandani M. , Mallick H.N. , Jagannathan N.R. , Mohan Kumar V.
Published: April 2003

A stereotaxic restraining assembly was designed and developed for simultaneous electrophysiological recordings and functional MRI (fMRI) data acquisition from a conscious rat. The design of the nonmagnetic stereotaxic apparatus facilitated the restraining of head and body of the unanesthetized conscious animal during MRI experiments. The apparatus was made of Teflon and Perspex materials with an appropriate size and shape for a 4.7 T / 40 cm animal MRI scanner. Electrodes made from nonmagnetic silver wire were implanted on the skull for recording the electroencephalogram (EEG), the electro‐oculogram (EOG), and the electromyogram (EMG), while polycarbonate screws were used for anchoring the electrode assembly. There were no major distortions or artifacts observed in the electrophysiological tracings and MR images. Electrophysiological recordings during fMRI acquisitions are useful to study different neurophysiological mechanisms of sleep and pathophysiology of seizure activity. Integration of electrophysiological recordings (with their good temporal resolution) and MRI (with its superior spatial resolution) is helpful in characterizing the functional state of different brain regions. Magn Reson Med 49:962–967, 2003. © 2003 Wiley‐Liss, Inc.
A numerical model for the cyclic deterioration of railway tracks
Authors: Suiker Akke S. J. , de Borst René
Published: April 2003

An elasto‐plastic material model is proposed that can be used to simulate the cyclic deterioration of railway tracks. The model describes the envelope of the irreversible, plastic material response generated during a cyclic loading process, thereby distinguishing the mechanisms of frictional sliding and volumetric compaction. The reversible response is represented by a pressure‐dependent, hypo‐elastic material law. After the numerical integration of the model is specified, the model is calibrated on laboratory experiments and employed in a finite‐element case study of the long‐term settlement behaviour of a railway track. The main features of the model are illustrated by comparing the computed response with the response obtained by in situ track measurements. Copyright © 2003 John Wiley & Sons, Ltd.
An arbitrary Lagrangian–Eulerian finite element method for finite strain plasticity
Authors: Armero Francisco , Love Edward
Published: April 2003

This paper presents a new arbitrary Lagrangian–Eulerian (ALE) finite element formulation for finite strain plasticity in non‐linear solid mechanics. We consider the models of finite strain plasticity defined by the multiplicative decomposition of the deformation gradient in an elastic and a plastic part (F = FeFp), with the stresses given by a hyperelastic relation. In contrast with more classical ALE approaches based on plastic models of the hypoelastic type, the ALE formulation presented herein considers the direct interpolation of the motion of the material with respect to the reference mesh together with the motion of the spatial mesh with respect to this same reference mesh. This aspect is shown to be crucial for a simple treatment of the advection of the plastic internal variables and dynamic variables. In fact, this advection is carried out exactly through a particle tracking in the reference mesh, a calculation that can be accomplished very efficiently with the use of the connectivity graph of the fixed reference mesh. A staggered scheme defined by three steps (the smoothing, the advection and the Lagrangian steps) leads to an efficient method for the solution of the resulting equations. We present several representative numerical simulations that illustrate the performance of the newly proposed methods. Both quasi‐static and dynamic conditions are considered in these model examples. Copyright © 2003 John Wiley & Sons, Ltd.
A collocation meshless method based on local optimal point interpolation
Authors: Zuppa Carlos , Cardona Alberto
Published: April 2003

This paper deals with the use of the local optimal point interpolating (LOPI) formula in solving partial differential equations (PDEs) with a collocation method. LOPI is an interpolating formula constructed by localization of optimal point interpolation formulas that reproduces polynomials and verifies the delta Kronecker property. This scheme results in a truly meshless method that produces high quality output and accurate solutions. Copyright © 2003 John Wiley & Sons, Ltd.
A priori error estimator of the generalized‐α method for structural dynamics
Authors: Chung Jintai , Cho Eun‐Hyoung , Choi Keeyoung
Published: April 2003

An a priori error estimator for the generalized‐α time‐integration method is developed to solve structural dynamic problems efficiently. Since the proposed error estimator is computed with only information in the previous and current time‐steps, the time‐step size can be adaptively selected without a feedback process, which is required in most conventional a posteriori error estimators. This paper shows that the automatic time‐stepping algorithm using the a priori estimator performs more efficient time integration, when compared to algorithms using an a posteriori estimator. In particular, the proposed error estimator can be usefully applied to large‐scale structural dynamic problems, because it is helpful to save computation time. To verify efficiency of the algorithm, several examples are numerically investigated. Copyright © 2003 John Wiley & Sons, Ltd.
Sedimentation and diffusion of cellulose molecules
Authors: Hermans J. J.
Published: April 2003

It is shown that the sedimentation and diffusion constants of cellulose at infinite dilution conform with a formula derived on the assumption of randomly coiled structures. The principle is introduced that the sedimentation velocity of closely packed particles moving through a liquid exerts an influence on their motion, according to known hydrodynamic laws.
Silver dichroism of micellar systems with fibrous structures
Authors: Frey‐Wyssling A. , Wälchli O.
Published: April 2003

By embedding submicroscopic silver rodlets in micellar systems with fibrous structures, unexpectedly strongly anisotropic rodlet compounds bodies are formed. The observed dichroism, indigo blue–straw yellow, suggests the possibility that a particular anisotropic modification of silver is being dealt with, instead of cubic silver. On applying Wiener's compound body formulas, it appears, however, that in the short‐wave region the observed anisotropic effects (negative rodlet double refraction and dichroism) can be computed from the optical properties of isotropic silver. In the spectral region of the average and long waves, differences are found between the observed anisotropy and the value calculated by means of Wiener's formulas. These differences are, however, not of such a nature that it is necessary to assume an unknown allotropic modification of silver with particular optically anisotropic properties in order to explain them.
Determination of persulfate in emulsion polymerization latices
Authors: Kolthoff I. M. , Guss L. S. , May D. R. , Medalia A. I.
Published: April 2003

In the emulsion polymerization of butadiene, styrene, or both, potassium persulfate is often used as the catalyst. A convenient concentration of potassium persulfate in the aqueous layer of the charge is 0.10–0.2%; the method of analysis should therefore be suitable for very small persulfate concentrations. Three methods have been investigated. In the volumetric method the persulfate is allowed to react in an acid medium with an excess of standard ferrous iron, the excess being back‐titrated after a given period of time with standard ceric cerium solution. The recommended procedure was found accurate and precise within 0.5%, even at such small concentrations as 5 mg. of potassium persulfate per 100 ml. When latex is analyzed by this method, the polymer is first removed by coagulation with sulfuric acid and the persulfate determined in the filtrate. In order to obtain reliable results the reaction between the persulfate and ferrous iron in the filtrate must be carried out in the absence of oxygen, although this is not necessary in solutions of pure persulfate. The interference by oxygen is attributed to substances of peroxidic character in the fatty acid soaps used as emulsifiers in the emulsion polymerization. The colorimetric method (“Becco” method) is based upon the oxidation of the leuco base of commercial wool green BSMA to a green dye by the persulfate and (colorimetric) measurement of the dye formed. The various factors affecting the accuracy and precision of this method have been investigated and a procedure is given for the analysis of latex. For several reasons, the volumetric and polarographic methods are superior to the colorimetric method. Persulfate in a latex can be determined accurately by polarographic analysis of the latex filtrate after removal of the polymer with sulfuric acid. The polarographic determination can be carried out, in the presence of oxygen, with simple equipment. The method is rapid and precise.
Preparation and properties of rubberlike high polymers. II. Polymerization of mixtures in bulk
Authors: Koningsberger C. , Salomon G.
Published: April 2003

Mixtures of butadiene and dimethylbutadiene with varying quantities of styrene and acrylonitrile have been copolymerized under various catalytic conditions at 100°C. The formation of cyclic dimers from dienes and vinyl compounds is, in some cases, much more pronounced than the dimerization of the dienes alone. Since the latter is also a kind of Diels‐Alder reaction, a series with increasing dienophilic properties can be established from a comparison of the yields of cyclic dimers. From solubility and swelling experiments it is evident that the polymers prepared from butadiene and the vinyl compounds and those from dimethylbutadiene and acrylonitrile are true copolymers. The mechanical properties of the copolymers from butadiene and increasing amounts of a vinyl compound change gradually from those of a rubber to those of the polyvinyl compound. The copolymers from a mixture containing 30% styrene or acrylonitrile are very similar, respectively, to Buna S and Perbunan. Copolymers of the same composition from dimethylbutadiene and acrylonitrile, on the other hand, form a new class of thermoplastics with a much higher temperature of elasticity.
New method for determination of the activation energy for the gelation of silicic acid solutions
Authors: Penner S. S.
Published: April 2003

A new method for the determination of the activation energy for the setting of silicic acid solutions is described. Experimental results point to the conclusion that setting to a gel occurs at a definite stoichiometric point which is independent of temperature.
Reactivity of monomers in copolymerization
Authors: Nozaki Kenzie
Published: April 2003

An investigation of the copolymerization of many monomer pairs induced by benzoyl peroxide has shown that an order of monomer reactivity with radicals exists. By utilizing the data available, it was possible to make a semiquantitative arrangement of many monomers according to their relative rates of reaction with radicals. A symmetrical selectivity factor is assumed to account for deviations from the order in copolymerization reactions. This selectivity may be attributed to (1) complex formation between monomers or to (2) dipole, steric, or other factors which are independent of concentration. Copolymerization equations have been derived for each case and application of them to styrene–methyl methacrylate mixtures has indicated that selectivity due to (2) is most important in this system. The equation for case (2) has been applied to other copolymer systems.
Water‐soluble alkoxyacetals of polyvinyl alcohol
Authors: Beal K. F. , Thor C. J. B.
Published: April 2003

Polyvinyl alcohol may be reacted with methoxyacetaldehyde, 2‐methoxyethoxyacetaldehyde, 2‐methoxyethoxyacetaldehyde, 2‐n‐propoxyethoxyacetaldehyde, tetrahydrofurfuryloxyacetaldehyde, or 3‐methoxypropionaldehyde, or with mixtures of these aldehydes, to yield thermoplastic resins which are soluble in cold water below specific temperatures peculiar to each resin, and which are soluble in most organic solvents except aliphatic hydrocarbons.
Polymerization of olefins and diolefins in suspension and emulsion. Part II
Authors: Hohenstein W. P. , Mark H.
Published: April 2003

This and a previous article (p. 127) review the literature from 1910‐1945 on polymerization of olefins and diolefins in suspension and emulsion, and present a number of new measurements not published to date. The subject is considered mainly from the point of view of scientific information on the mechanism of polymerization in aqueous suspensions and emulsions, but brief mention is also made of the more important disclosures in the patent literature. The new data presented in this article refer to (1) initial rates of polymerization of styrene, methyl methacrylate, vinyl acelate and acrylonitrile in aqueous suspensions and in soap emulsions as a function of catalyst concentration, temperature, and soap concentration; (2) influence of water‐soluble activators, such as sodium bisulfite; (3) influence of initial size of monomer droplets on initial rates of monomer consumption; (4) study, with the aid of the electron microscope, of size of monomer droplets and polymer particles throughout polymerization; and (5) a few experiments on side reactions in the domain of higher conversions. No attempt is made in this paper to review and appraise the very large number of recent patents (from about 1930 on), which protect special procedures on the use of various promoting, regulating, or modifying ingredients. A complete digest of this practice does not exist at present, but reference may be made to the excellent chapter on emulsion polymerization in the book of Talalay and Magat, to the very valuable compilation of patents by Hoseh, and to the enumeration of a selected number of patents in the book of Scheiber.1
Refractometric determination of second‐order transition in polyvinyl acetate
Authors: Wiley Richard H.
Published: April 2003

The refractive index‐temperature data for polyvinyl acetate show a second‐order phase transition temperature of 24°C.
Chain structure of vinyl and diene polymers in relation to polymerization mechanism
Authors: Flory Paul J.
Published: April 2003

The usual occurrence of structural units of vinyl polymers in head‐to‐tail sequence is attributed to the stabilization of the free radical of the growing polymer chain by the monomer substituent(s). Addition at the unsubstituted carbon of the vinyl group reproduces a free radical of lower energy than does addition at the substituted carbon. In at least one instance (vinyl acetate polymerization) a very small percentage of head‐to‐head addition takes place in spite of this energy difference. These ideas can be extended to polymers of dienes. Here the problem is complicated by the simultaneous occurrence of 1,2 (or 3,4) as well as 1,4 addition. In the case of an unsymmetrical diene monomer such as isoprene it is possible, from detailed examination of the structure of the polymer, to distinguish between preferred addition at carbon atoms 1 and 4 of the monomer.
Mercaptans as promoters and modifiers in emulsion copolymerization of butadiene and styrene using potassium persulfate as catalyst. I. Mercaptans as promoters
Authors: Kolthoff I. M. , Harris W. E.
Published: April 2003

The rate of emulsion copolymerization of butadiene and styrene, with soap as emulsifier and potassium persulfate as catalyst, is extremely small at 50°C. The presence of very small amounts of high‐molecular mercaptans promotes the copolymerization reaction. The promoting effect is at a maximum for primary, secondary, and tertiary dodecyl mercaptans and decreases for mercaptans of either higher or lower molecular weight. The promoting effect is independent within wide limits of the amount of mercaptan added after the minimum quantity has been exceeded. Mercaptans which are poor promoters may be so because they fail to bring about chain initiation or because they aid in chain termination. The low‐molecular mercaptans which are poor promoters prevent the high‐molecular mercaptans from exerting their good promoting effect when a mixture of both types of mercaptans is used. The mechanism of the promoting effect of mercaptans upon the emulsion copolymerization of butadiene (75 parts) and styrene (25 parts) or upon the polymerization of butadiene alone is not yet clear.
Copolymerization. I. Kinetics and some experimental considerations of a general theory
Authors: Melville H. W. , Noble B. , Watson W. F.
Published: April 2003

A review of theoretical progress in copolymerization has shown that the results of previous authors are consistent and equivalent. A general scheme of copolymerization has been stated and its kinetic consequences worked out. The rate expressions have been derived for percentage polymerization against time, and initial rate against initial monomer concentration. Some experimental considerations have been given. The advantages of photochemical technique have been stressed, physical means of following the reaction outlined, and new methods of determining σ and μ described. Means of verifying the kinetics have been suggested, in particular the obtaining of the individual velocity constants. It is important to note in this connection, that further experiments to determine the lifetime of the growing polymer chain are not required.
Effect of centrifugal field on resistance to motion of threadlike molecules in solution
Authors: Singer Seymour J.
Published: April 2003

An attempt has been made in this communication to formulate explicitly the dependence of the frictional coefficients of threadlike molecules in solution upon the centrifugal field applied to them in the usual velocity ultracentrifuges. This quantitative treatment, using the Kuhn and Kuhn odel for randomly coiled free‐draining thread molecules, verifies the assumption generally made that the effect considered is negligible. Since the molecular weight of the particles and the magnitude of the centrifugal field applied to them vary inversely with each other, the constant, \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\beta h_0^2 }$\end{document} rarely attains values which are significant, and the effect produced by orientation of the threads is balanced by the effect due to stretching them. Moreover, by a suitable change of parameters, this treatment could be extended to account for the action of other tensile forces acting on thread molecules in solution
X‐ray and moisture equilibrium investigation of sodium pectate
Authors: Palmer K. J. , Shaw T. M. , Ballantyne M.
Published: April 2003

The variation of the x‐ray reflection to the interchain separation in sodium pectate has been determined as a function of moisture content. The crystalline regions in sodium pectate have been found to sorb about 24% water (dry basis) at a relative humidity of 95% at 25°C. The sample as a whole under these conditions has a water content of 64%. At high water contents, therefore, a large difference in water content must exist between the crystalline and amorphous regions of sodium pectate. A marked change in degree of crystallinity occurs, as determined by the number and sharpness of the x‐ray reflections, at an average water content of about 6% on desorption and on sorption at an average water content of about 14%.
Heats of combustion and solution of liquid styrene and solid polystyrene and heat of polymerization of styrene
Authors: Roberts Donald E. , Walton William W. , Jessup Ralph S.
Published: April 2003

Bomb calorimetric measurements have yielded for the heats of combustion (—ΔHoc) at 25°C. of liquid styrene and solid polystyrene to form gaseous carbon dioxide and liquid water the values 4394.88 ± 0.67 int. kjoule per mole (1050.58 ± 0.14 kcal. per mole), and 4325.09 ± 0.42 int. kjoule per C8H8 unit (1033.89 ± 0.10 kcal. per C8H8 unit), respectively, and for the heat of polymerization of liquid styrene to solid polystyrene at 25°C. the value 69.79 ± 0.66 int. kjoule per mole (16.68 ± 0.16 kcal. per mole). The results obtained on two samples of polystyrene of different molecular weight were in agreement within the precision of the measurements. Measurements of the heat of solution of solid polystyrene in liquid monomeric styrene gave the value 3.59 ± 0.21 int. kjoule (0.86 ± 0.05 kcal.) evolved per C8H8 unit of polystyrene at 25°C. Addition of this to the value for the heat of polymerization of liquid styrene to solid polystyrene gives the value 73.38 ± 0.69 int. kjoule (17.54 ± 0.16 kcal.) per mole of styrene for the heat of polymerization of liquid styrene at 25°C., when the final product is a solution of polystyrene in styrene containing 6.9% by weight of polystyrene.
Light‐induced polymerization of some monomers containing allyl and methacrylate groups
Authors: Cohen S. G. , Ostberg B. E. , Sparrow D. B. , Blout E. R.
Published: April 2003

In the polymerization of ally1 methacrylate in the presence of benzoyl peroxide at 75°C., gelation occurs after about 6% reaction. By carrying out the polymerization a t 1°C. to 25°C. in the presence of biacetyl or benzoyl peroxide and photoflood or ultraviolet radiation, we have been able to postpone gelation until 19 to 39% reaction. In the presence of biacetyl the extent of reaction a t the gel point is increased as the temperature is lowered and as the light intensity is raised.

Biacetyl is activated by radiation in the 400–460 mμ region; benzoyl peroxide is activated by radiation in the 350–380 mμ region.

Hydrolysis and bromination of the soluble polymer did not indicate any marked difference in the composition of the samples prepared at 75°C. and 15°C. The soluble polymer which is prepared at 75°C. appears to have an intrinsic viscosity which may be three to twenty times as great as that of the polymer which is prepared at 1–25°C.

The polymerization of methyl methacrylate and allyl acetate under the two sets of conditions indicated that the reaction of the methacrylate was affected more than that of the allyl compound by the change in conditions. The copolymerization of methyl methacrylate and allyl chloroacetate indicated that somewhat more allyl monomer was incorporated into the copolymer at the lower temperature than a t the higher temperature.

The increased extent of reaction at the gel point at the lower temperatures appears to be due almost entirely to diminished molecular weights. The decrease in molecular weight a t low temperatures is probably due to the decreased rate of chain growth, the rate of initiation remaining high because of irradiation, and the rate of termination being little dected because of its low activation energy. The effects of temperature on the composition of the copolymer, and of molecular weight on the point of gelation, are discussed briefly.
Magnetic rotatory power of liquid polymers
Authors: Lagemann Robert
Published: April 2003

The Verdet constants of nine polyethylene glycols, three polypropylene glycols, and nine silicone polymers have been measured at 25°C. It was found that the Verdet constant increases with increase in molecular weight in each of the series, and approaches a constant value. A similar increase in the molecular magnetic rotation was noted. The results are in contrast with those on polystyrene, and the effect of end groups on the measurements is discussed in explanation.
Stress‐strain characteristics of guaran triacetate
Authors: Smart Charles L. , Whistler Roy L.
Published: April 2003

Guaran triacetate, a linear molecule having one‐unit branches, can be cast into clear, colorless films having a tensile strength of 7.5kg./mm.2 and an elongation at break of 4%. Thus, it appears that one‐unit branches of the size of the glycosidic unit do not adversely affect the film‐formingproperties of polysaccharide acetates. Plasticized films show more elasticity and greater elongation at break.
Simple presentation of network theory of rubber, with a discussion of other theories
Authors: James Hubert M. , Guth Eugene
Published: April 2003

The approximations implicit in the use of the Gaussian network model for soft rubber are discussed. It is shown that the form of the stress–strain curve can be derived for this model simply, and without special assumptions about the form or behavior of the network. The common assumption that the network junctions are fixed, or can be treated as fixed, is discussed. It is shown that this picture of the situation is unrealistic: the junctions have a Brownian motion comparable to that of any portion of the intervening molecular segments. The introduction of this assumption is not generally admissible, but it will not affect the outcome of certain types of calculation; in particular, one can foresee that it need not affect the calculated form of the stress‐strain curve. A particularly simple and straightforward calculation of the network entropy on this basis is given. Wall's the ory of rubber is analysed. It is shown that Wall's postulates are not consistent with the network structure of rubber, and in general lead to different results.
Water content of hydrophilic phenol‐formaldehyde resins: Vapor pressure‐temperature relationships
Authors: Bentz Ralph W. , Neville Harvey A.
Published: April 2003

The significance of the water content to the physical properties of phenol‐formaldehyde resins at various stages of preparation is briefly discussed. Available methods for the determination of water in such resins were found to be either unreliable or too elaborate for process control. It was undertaken to develop a simple, rapid, relative method for the continuous measurement of water content which can be used to follow the follow the process of dehydration and to indicate the end‐point which will result in the best dispersion of water in the cured resin. In order to standardize or calibrate such a relative method, it was necessary also to develop an absolute method for the analysis of water in the resol.

The composition of a homogeneous mixture of liquids is reflected by its vapor pressure‐temperature relationships. During dehydration at 80°C., the vapor pressure of the resol decreases about 350 mm. of mercury. A very sharp increase in the slope of the vapor pressure curve occurs at approximately the proper degree of dehydration. At this stage a slight decrease in water content causes a very large decrease in vapor pressure. The sharp inflection in the curve is attributed to the existence of both “free” and “bound” water in the resin.

During the process of vacuum dehydration of the resin, while the “free” water decreases to approximately one‐eighth of its original content, the “bound” water remains substantially constant. The binding of water is attributed to the methylol groups of the resol molecules and its release during the cure or hardening of the resin is considered to result from the conversion of these groups to methylene linkages.
Koresin and related resins
Authors: Marvel C. S. , Gander Robert J. , Chambers R. R.
Published: April 2003

The infrared and ultraviolet absorption spectra of Koresin are very similar to those of an acid‐catalyzed p‐tert‐butylphenol‐acetal‐ dehyde polymer. This is believed to be evidence that Koresin has Structure I. A variety of phenol‐aldehyde resins have been prepared for comparison with Koresin. The ratings of some of these materials as tackifiers have been reported. These furnish further evidence that the molecular weight of a phenol‐aldehyde resin is important in its tackifying action. An alkaline‐catalyzed condensation product of acetylene and p‐tert‐butylphenol shows no tackifying action and has no free hydroxyl in the polymer as judged by its infrared pattern.
Ultraviolet absorption spectra of some copolymers containing acenaphthylene, and of related compounds
Authors: Herington E. F. G. , Jones J. Idris
Published: April 2003

The strong ultraviolet absorption in the wave‐length region 280‐330 mμ shown by copolymers of acenaphthylene with styrene or methyl methacrylate is due to acenaphthylene residues. The spectra of samples of copolymer containing a small percentage of acenaphthylene are different from the spectrum of polyacenaphthylene. As a result of the comparison of the spectra of these copolymers with the spectra of acenaphthene and with the two forms of 1,1′‐biacenaphthyl it is concluded that spectra of the copolymers can be explained as arising from the presence of pairs of acenaphthylene groups. Finally it is shown that the spectra can be used to estimate the acenaphthylene contents of the copolymers.
Rheology of thermoplastics. II. Recoverable and nonrecoverable deformations of polystyrene between 90 and 240°C. as a function of molecular weight
Authors: Buchdahl R. , Nielsen L. E. , Merz E. H.
Published: April 2003

The rheological properties of polystyrene have been studied between 90 and 240°C. as a function of molecular weight. Three different methods have been used to obtain the data: rotational viscometer, extrusion‐type capillary viscometer, and tensile creep measurements. It has been shown that the nonrecoverable (viscous) deformation is a function of molecular weight whereas the recoverable deformations are, within the investigated molecular weight range, practically independent of chain length. An explanation of this observation is suggested, based on the assumption of a labile network structure, which explains also the effect of “previous history” on the recoverable deformations. The temperature dependence of the recoverable and nonrecoverable deformations is shown to be very similar. Experimental evidence is presented to show that the dependence of the viscosity on shear stress (or rate of shear) is not a simple power relationship but is of the sigmoidal type. It is shown that the creep or compliance function a few degrees below the second‐order transition point does not depend on the weight‐ or number average molecular weight.
Structure and thermodynamics of elastomeric microgel
Authors: Medalia A. I.
Published: April 2003

Microgel consists of branched molecules of colloidal dimensions, formed by gelation occurring within the confines of a latex particle. It is shown that microgel should be (thermodynamically) soluble but, because of the large sue of each molecule, it settles out of solution. The proportion of subchains which are connected to centers of cross‐linkage at one end rather than both ends is calculated for gelled molecules of various values of the branching coefficient.
Determination of microgel in GR‐S rubber
Authors: Medalia A. I. , Kolthoff I. M.
Published: April 2003

Microgel consists of branched molecules of colloidal dimensions, formed by gelation occurring within the confines of a latex particle. Thermodynamically, microgel is expected to be soluble in a “good” solvent, such as benzene. Experimentally, it is found that carefully dried microgel‐containing polymers are completely soluble in benzene. Detection of microgel by solubility measurements requires the conversion of microgel to macrogel (gel of macroscopic dimensions) prior to the solubility measurement. This can be accomplished by heating under a variety of conditions. Milling of the polymer before heating aids in this conversion.

A Standard Procedure is recommended for the determination of microgel in standard GR‐S rubber: the polymer (preferably coagulated in ethanol) is milled for about 10 passes, with the addition of 2% of phenyl‐beta‐naphthylamine; the milled polymer is heated for 12 hours in a vacuum oven at 80°, then placed inside a box of wire screen and immersed in benzene for 40 hours to extract the sol portion.

Solutions of microgel in benzene can be fractionally precipitated by addition of ethanol or nitroethane. The fractionation is, primarily according to molecular weight rather than degree of cross‐linkage. Viscosity and light‐scattering measurements of the fractions show that the polymers are of high molecular weight and are cross‐linked.
Polyelectrolytes. VIII. Quaternized polyesters of succinic anhydride and methyldiethanolamine
Authors: Fuoss Raymond M. , Edelson David
Published: April 2003

Linear polyelectrolytes have been prepared by quaternizing with methyl bromide the polyester obtained by condensation between succinic anhydride and methyldiethanolamine. Molecular weights, determined by end group titration, were in the range 2000‐43,000. The polysalts hydrolyze in water but are stable in absolute methanol. Viscosities in methanol of the polysalt of highest molecular weight conform to the empirical equation:

Conductance curves are sharply concave upward on a Λ − c1/2 scale, indicating a high degree of association of counter ions with the polycation at finite concentrations. Estimates of limiting mobility suggest a curved rodlike structure for the polycation at infinite dilution.
Adhesion of polyethylene and polystyrene to steel
Authors: Kraus Gerard , Manson James E.
Published: April 2003

A conservative estimate of the molecular forces involved in the adhesion of polymers to conducting surfaces leads to bond tensile strengths considerably above those realizable in practice. This is explained by the occurrence of flaws, thermal stresses, and deformation under load. In order to minimize these factors, very thin films of polystyrene and polyethylene were molded between steel cylinders and experimental conditions were carefully controlled with the result that joint strengths in excess of bulk tensile strengths were obtained. Curves of joint failure stress versus film thickness at various temperatures are given, and extrapolated to zero thickness. The extrapolated adhesion values represent a lower limit of the specific adhesion. At 25°C. they are 183 kg./cm.2 for polyethylene, and 412 kg./cm.2 for polystyrene.
Physical characterization of cellulose xanthate in solution
Authors: Tait C. W. , Vetter R. J. , Swanson J. M. , Debye P.
Published: April 2003

The intrinsic viscosity of cellulose xanthate solutions was studied as a function of the electrolyte content of the solvent, and found to decrease sharply with increase in electrolyte concentration. All electrolytes tested except sodium and lithium hydroxides produced essentially the same reduction in intrinsic viscosity for solutions of equivalent ionic strenghts, indicating that the effect was largely one of interaction between the solvent ions and the charged xanthate groups. Hydroxides induced a greater viscosity reduction. The reason for this was not fully resolved; however, indications were obtained that the hydroxides, in addition to behaving as electrolytes toward the charged xanthate groups, also interact with the hydroxyl groups on the parent cellulose chain.

Light scattering measurements, as well as data on the variation of the intrinsic viscosity with molecular weight in various solvents, showed that the change in intrinsic viscosity with electrolyte concentration could be accounted for by a change in configuration, or degree of coiling of the molecule. Calculations indicated that in pure water cellulose xanthate should approach a rigid rod configuration whereas in 6% caustic coiling occurs and the molecule resembles more a random configuration.
Solutions of polyelectrolytes and mechanochemical systems
Authors: Katchalsky A.
Published: April 2003

The behavior of polyelectrolyte molecules in aqueous solution has been discussed. It has been shown that the pronounced increased in viscosity of polymeric acids upon ionization is due to the change of shape of the molecule due to electrostatic repulsive forces. Nonionized polymeric acids assume the form of highly hypercoiled rigid spheres obeying Einstein's viscosity law, the hypercoiled form being presumably due to strong intermolecular hydrogen bonding and van der Waals' interactions. The polymeric molecules open up with increasing ionization, and assume the form of freely linked threads, obeying Staudinger's law, at about 10% ionization. At high degrees of ionization, they stretch to rod‐like filaments, with the viscosity increasing as the square of the molecular weight. The shape of the molecules is also dependent on the concentration of the solution and on the amount of foreign ions present. An excess of the latter annihilates the electrostatic field and reduces the viscosity to that of normal random coils. Polyampholytes of the type of copolymers of methacrylic acid and vinylpyridine show the expected behavior: the viscosity is at a minimum at the isoelectric point and increases in both the acidic and alkaline regions with the increase in free charge.

The field energy of polyelectrolyte molecules has been determined thermodynamically by means of the potentionmetric titration. It has been shown to be dependent upon the molecular weight, the concentration of the polymer, and the ionic strength. The charge of the field energy per ionized group has been found to be independent of the molecular weight.

The electrostatic field energy has been calculated theoretically from statistical and electrostatic considerations and an approximated formula has been arrived at by using a simplified model. The calculated field energies have been compared with those derived from potentiometric titration and found to be in good agreement with each other.

The deviations from the theory, the particular shape of the viscosity versus degree of ionization, and field energy versus ionization curves, have been attributed mainly to the existence of contractile van der Waals' forces, operative between the segments of the polymeric molecules. These forces act in addition to the usual rubberlike configurational elasticity. An attempt has been made to explain these effects on a quantitative basis.

Mechanochemical systems capable of transforming chemical energy of ionization into mechanical energy of stretch have also been described. These systems, typified by cross‐linked gels and fiber gels of polymeric electrolytes, can be made to work in isothermal cycles in a manner reminiscent of the physicochemical mechanism of the muscle. A cycle has been analyzed in which a system is made to work between two pH values (corresponding to chemical potentials), and two degrees of ionization, under the influence of an exterior force.
Thermodynamics and mechanics of filler reinforcement
Authors: Rehner John
Published: April 2003

Following a brief review of some earlier theories of filler reinforcement that were based, at least partly, on thermodynamic treatments, a reinforcement equation is derived by a combination of thermodynamics and the elasticity theory of large strains. It consists of an elastic energy term and a surface energy term, and is given by:

In it, the “reinforcement energy,” R.E., is defined as the energy of the filler‐rubber mixture less that of the separate components. This is related to a fractional heat term (p) arising from the “expansion” of the rubber due to filler incorporation, the Young's modulus (E) of the rubber, the number of particles (n) of filler (considered as existing initially in an aggregate), the ultimate particle diameter (d), the volume of rubber (V1), the total energy of immersion per unit surface area (Γ) of the filler in the rubber, and the mean cohesion or aggregation energy per particle (δ) between the particles in the original aggregate.

The significance of R.E. in terms of actual reinforcement is discussed; R.E. is regarded as negative measure of reinforcement. Estimates are made of the magnitudes of the two energy terms and of the surface energies Γ and δ. These indicate that in mixtures containing very active fillers (such as carbon blacks in natural rubber), Γ is of the order of 100 ergs per sq. cm. and the surface energy term is dominant. A crude estimate indicates that δ is much less than Γπd2 for very active fillers, that these quantities may be of the same order of magnitude for less active fillers, and that δ may be larger than Γπd2 for inert fillers. In the last two cases, the surface energy term loses much or all of its dominant character.

Predictions from the reinforcement equation are examined in the light of available experimental results, and some apparent discrepancies are discussed. Expressions are given for corrections that need to be applied to the equation when particle dispersion is incomplete, or when the latter is a function of the filler concentration.
The counterion distribution in solutions of rod‐shaped polyelectrolytes
Authors: Alfrey Turner , Berg Paul W. , Morawetz Herbert
Published: April 2003

For solutions containing rod‐shaped polyelectrolytes and their counterions only, the Poisson‐Boltzmann equation can be solved explicity without the usual assumption of the Deybe‐Hückel theory. At charge densities corresponding to half‐neutralized polyacrylic acid a large proportion of monovalent counterions is located close to the polyion even in solutions as dilute as 1/800 base molar.
Catalytic conversion of a diene into deeply colored polymers
Authors: Eisler B. , Farnsworth S. D. , Kendrick E. , Schnurmann R. , Wassermann A.
Published: April 2003

Cyclopentadiene can be catalytically converted into a deep red polycyclopentadienetrichloroacetic acid adduct (I). Oxidation and hydrogenation experiments show that each repeating unit of (I) contains one double bond. Other observations, including spectroscopic and electrochemical measurements indicate that these double bonds are conjugated, and that this polymerization involves the migration of hydrogen atoms. The kinetics of the formation of (I) are investigated and some results of these measurements, together with those pertaining to the alkaline hydrolysis of (I), make it probable that the initiation step is in acid‐catalyzed esterification of the diene and that the final polymer is an ester. Colloid chemical properties of (I) are described.
Etude thermocinétique de l'adsorption. Cas des corps solubles et des substances macromoléculaires
Authors: Calvet Edouard
Published: April 2003

L'étude thermocinètique de l'adsorption et celle de la chaleur dégagée en fonction de la masse du corps adsorbé par unité de masse de l'adsorbant réalisées au microcalorimètre (spécialement adapté à la mesure des phénomènes lents) nous parait présenter un grand intérêt: pour les corps insolubles ces études permettent l'évaluation des surfaces des poudres, la mesure approximative de la vitesse d'expansion des films, l'étude de la fraction activée des surfaces; pour les corps solubles elles permettent de mettre en évidence le phénomène très général de l'adsorption qui précède la dissolution et d'interpréter le mécanisme de la dissolution; pour les substances macromoléculaires elles permettent de classer les solvants ou gélatinisants suivant leur activité, d'étudier le gonflement, les complexes de solvatation, etc. Tout cela démontre le nécessité d'organiser des Centres bien équipés de microcalorométrie des phénomènes lents.
Method of colloid titration (a new titration between polymer ions)
Authors: Terayama Hiroshi
Published: April 2003

A general discussion about the method of colloid titrations is given in this report. A new titration method is based on the stoichiometric combination of positive and negative colloid ions. The end point is decided by indicators (known as metachromatic coloring matters) like toluidine blue. The standard colloid reagents are P.V.S.‐K (potassium salt of polyvinyl alcohol sulfate) and Macramin (N‐polymethylated chitosan derivatives). The typical operations of this method are described briefly: the direct, indirect, and differential titration methods. The colloid titration curve is somewhat different from the acid‐base titration curve obtained potentiometrically, but it is characteristic and reproducible under definite conditions and so it is useful in quantitative and qualitative analysis. This titration may be carried out even under extraordinary dilute conditions (5 × 10−4 N) and the entire process is quite similar to the usual acid‐alkali titration. The precision is below ±ca. 5% if the method is carefully followed.