bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein phosphatase 1cγ is required in germ cells in murine testis
Authors: Oppedisano‐Wells Leandra , Varmuza Susannah
Published: April 2003

The protein phosphatase 1cγ (PP1cγ) gene is required for spermatogenesis. Males homozygous for a null mutation are sterile, and display both germ cell and Sertoli cell defects. As these two cell types are physically and functionally intimately connected in the testis, the question arises as to whether the primary site of PP1cγ action is in Sertoli cells, germ cells, or both. We generated chimeric males by embryo aggregation to test whether wild type Sertoli cells are capable of rescuing mutant germ cells. To distinguish between the desired XY‐XY chimeras and uninformative XX‐XY chimeras, we designed an adaptation of the single nucleotide primer extension (SNuPE) assay. None of the XY‐XY chimeras sired pups derived from mutant germ cells, indicating that the protein is required in germ cells for production of functional sperm. Analysis of a chimeric testis revealed intermediate phenotypes when compared with PP1cγ−/− testes, suggestive of cell nonautonomous effects. We conclude that PP1cγ is required in a cell autonomous fashion in germ cells. There may be an additional cell nonautonomous role played by this gene in testes, possibly mediated by defective signaling between germ cells and Sertoli cells. Mol. Reprod. Dev. 65: 157–166, 2003. © 2003 Wiley‐Liss, Inc.
Expression of vascular endothelial growth factor and its receptors in the rhesus monkey (Macaca mulatta) endometrium and placenta during early pregnancy
Authors: Wang Hongmei , Li Qinglei , Lin Haiyan , Yu Xiaodong , Qian Dong , Dai Jiejie , Duan Enkui , Zhu Cheng
Published: April 2003

Vascular endothelial growth factor (VEGF) is fundamental for development and maintenance of endometrial and placental vascular function during pregnancy. While there are a number of studies on VEGF in the human placenta, they are mostly restricted to late pregnancy. To further understand the role of VEGF in mediating angiogenesis during human early pregnancy, we employed a rhesus monkey early pregnancy model to study the temporal and spatial expression of VEGF and its receptors, fms‐like tyrosine kinase (Flt)‐1, and kinase‐insert domain‐containing receptor (KDR) mRNAs and proteins in the uteri on day 12, 18, and 26 of pregnancy using in situ hybridization, RT‐PCR, and immunohistochemistry. VEGF mRNA had been identified in the luminal epithelium on day 12, in the glandular epithelium on day 12 and 18, and the highest expression was detected in the walls of some spiral arterioles adjacent to the implantation site on day 18, in the placental villi and in the fetal‐maternal border on day 18 and 26. Besides, immunostaining of VEGF was detected in the placental villi and endometrial compartments including spiral arteries walls and the glandular epithelium. The localization of VEGF in the endothelium correlates with the presence of Flt‐1 and KDR receptors on vascular structure. All the results above suggest that VEGF‐VEGFR pairs were involved in the process of trophoblast invasion, maternal vascular transformation, and fetoplacental vascular differentiation and development during the rhesus monkey early pregnancy. Expression of VEGF, Flt‐1, and KDR in the epithelial cells also hints some additionally functional roles of VEGF during early pregnancy. Mol Reprod. Dev. 65: 123–131, 2003. © 2003 Wiley‐Liss, Inc.
Imaging single mammalian cells with a 1.5 T clinical MRI scanner
Authors: Foster‐Gareau Paula , Heyn Chris , Alejski Andrew , Rutt Brian K.
Published: April 2003

In the present work, we demonstrate that the steady‐state free precession (SSFP) imaging pulse sequence FIESTA (fast imaging employing steady state acquisition) used in conjunction with a custom‐built insertable gradient coil and customized RF coils can be used to detect individual SPIO‐labeled cells using a commonly available 1.5 T clinical MRI scanner. This work provides the first evidence that single‐cell tracking will be possible using clinical MRI scanners, opening up new possibilities for cell tracking and monitoring of cellular therapeutics in vivo in humans. Magn Reson Med 49:968–971, 2003. © 2003 Wiley‐Liss, Inc.
Method for quantitative imaging of the macromolecular 1H fraction in tissues
Authors: Ropele Stefan , Seifert Thomas , Enzinger Christian , Fazekas Franz
Published: April 2003

A new method was developed for mapping the relative density of the macromolecular protons involved in magnetization transfer (MT). This method employs a stimulated echo preparation scheme in order to modulate the phase distribution within a spin ensemble. This labeled spin ensemble is then used as an intrinsic indicator, which is diluted due to magnetization exchange with macromolecular protons. A pulse sequence is presented which compensates for longitudinal relaxation, allows observation of the dilution effect only, and provides for calculation of parameter maps using indicator dilution theory. Compared to other quantitative MT techniques, neither additional relaxation time measurements nor knowledge regarding the lineshape of the macromolecular proton pool are required. Moreover, the inherent low specific absorption rate and the low sensitivity for B1 errors make this method favorable in a clinical setting. This sequence was used to measure the macromolecular proton density in cross‐linked bovine serum albumin. Using a navigated echo planar readout, the sequence was also employed to visualize the macromolecular content of human brain in vivo. Magn Reson Med 49:864–871, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of inversion recovery preparation schemes for lipid suppression in 1H MRSI of human brain
Authors: Ebel Andreas , Govindaraju Varanavasi , Maudsley Andrew A.
Published: April 2003

To reduce contamination from subcutaneous lipid regions in MR spectroscopic imaging (MRSI) of whole brain, lipid signals are often suppressed using T1 nulling methods. If a range of lipid T1 values is present, the suppression efficiency will be improved using multiple inversion recovery (MIR) preparation. This study compared single IR (SIR) and double IR (DIR) applied with a volumetric MRSI sequence at 1.5 T based on experimental measurement of lipid T1 and T2 relaxation rates. At short and medium echo times (TEs), an approximately 28–47% improvement in lipid suppression was achieved with DIR compared to SIR. However, it also led to a loss of 37–43% in signal‐to‐noise ratio (SNR) for metabolites. Thus, SIR appears to be the better choice for suppressing lipid signals and maintaining metabolite sensitivity. Magn Reson Med 49:903–908, 2003. © 2003 Wiley‐Liss, Inc.
Proton echo‐planar spectroscopic imaging with highly effective outer volume suppression using combined presaturation and spatially selective echo dephasing
Authors: Chu Archie , Alger Jeffry R. , Moore Gregory J. , Posse Stefan
Published: April 2003

A highly effective outer volume suppression (OVS) technique, termed spatially selective echo dephasing (SSED), which employs gradient dephasing of spatially selective spin echoes, is introduced. SSED, which is relatively insensitive to T1 dispersion among lipid signals and B1 inhomogeneity, was integrated with very high spatial resolution 2D proton echo‐planar spectroscopic imaging (PEPSI) to assess residual lipid bleeding into cortical regions in the human brain. The method was optimized to minimize signal refocusing of secondary spin‐echoes in areas of overlapping suppression slices. A comparison of spatial presaturation with single or double SSED, and with combined presaturation and SSED shows that the latter method has superior performance with spatially uniform lipid suppression factors in excess of 70. Metabolite mapping (choline, creatine, and NAA) with a 64 × 64 spatial matrix and 0.3 cm3 voxels in close proximity to peripheral lipid regions was demonstrated at 1.5 T with a scan time of 32 min using the standard head coil. Magn Reson Med 49:817–821, 2003. © 2003 Wiley‐Liss, Inc.
PUBS: Pulsatility‐based segmentation of lumens conducting non‐steady flow
Authors: Alperin Noam , Lee Sang Hoon
Published: April 2003

Dynamic velocity‐encoded phase‐contrast MRI (PC‐MRI) techniques are being used increasingly to quantify pulsatile flows for a variety of clinical applications. Studies suggest that the reliability of flow quantitation with PC‐MRI appears to be dominated by the consistency in the delineation of the lumen boundary. An automated method that utilizes both spatial and temporal information has been developed for improved accuracy and reproducibility. The method's accuracy was evaluated using a flow phantom with 8‐ and 5‐mm‐diameter lumens at two different flow rates. The reproducibility of the method was further evaluated with arterial, venous, and cerebrospinal fluid flow data from human subjects. The results were compared with measurements obtained manually by observers of different skill levels. Measurement values obtained manually were consistently smaller than those obtained with the pulsatility‐based segmentation (PUBS) method. For the 8‐mm lumen, significant improvements in measurement accuracy were obtained. Average lumen area measurement errors of about 18% for the high and low flows, obtained manually by a skilled observer, were reduced to 2.9% and 4.8%, respectively. For the 5‐mm lumen, the skilled observer underestimated the lumen area by 13%, while the PUBS method overestimated the lumen area by 28%. Overestimated lumen area measurements for the smaller lumen are attributed to the partial‐volume effect. There was significantly less measurement variability with the PUBS method. An average fourfold reduction in interobserver measurement variability was obtained with the new method. Magn Reson Med 49:934–944, 2003. © 2003 Wiley‐Liss, Inc.
Managing the impersonal in a personalized public service
Authors: Gretchen Kay
Published: April 2003

What happens when an apparently personalized small public service enters the information highway? How does it integrate the new frame of mind implied in the impersonal, open approach to information? The practical implications of implementing information technology as a means to use information strategically in the Maltese public service, with its apparently paradoxical administrative style, prompted the pilot study in early 2000 upon which this article is based. Using a simplified empirical approach, the study tested the hypothesis that small scale could affect the way leaders deal with the impersonal, such as information resource management. Although limited in scope, the results of the study support a qualified conclusion that small scale, through its link with personalization and associated informal mechanisms, does affect the way top managers in the public service deal with the impersonal, at least in the short and medium term. To what extent it does so, or the space for change, are subjects for further research. The article concludes with suggestions for further investigation into this topic, both in its narrow and wider applications. Copyright © 2002 John Wiley & Sons, Ltd.
Savings from integrating administrative systems for social assistance programmes in Russia
Authors: Jerome Gallagher L. , Struyk Raymond J. , Nikonova Ludmila
Published: April 2003

Russian local governments now have primary responsibility for the administration of social assistance programmes thanks to a combination of decentralization of some responsibilities from higher levels of government and the transfer of certain administrative functions from state enterprises to municipalities. Over the past few years, there has also been a distinct shift to means‐testing of social assistance. This article reports on the results of a pilot project undertaken to improve the efficiency of programme administration conducted in the city of Arzamas (pop. 110,000). The municipal administration promotes it as a programme to ease client burden and improve access to benefits. Specifically, the pilot introduced a unified application form for all the major social assistance programmes in the city and required, regardless of how many programmes are applied for, that applicants visit only one office and supply one set of documents verifying their eligibility for assistance. Benefit processing is also consolidated. Staff efficiency improvements are substantial: under the one‐window system, 127 benefits are processed per month per staff member, while 85 benefits were processed per month per staff member under the old administrative system. Impressive time savings for clients were also observed: the statistically average client saves between 1.3 and 2.4 hours, depending on the degree to which a client was able to coordinate documentation collection and trips to the benefit agencies under the old system. The total potential time saved by clients as a result of the one‐window reforms is between 4100 and 7600 person hours per month. Copyright © 2002 John Wiley & Sons, Ltd.
Nurturing knowledge: the UK Higher Education Links scheme
Authors: Eldridge Derek A. , Wilson Elisabeth M.
Published: April 2003

This article examines the development of academic networks and expertise through the UK Higher Education Links scheme, which is funded by the UK Department for International Development, managed by the British Council and supported by the principals of UK higher education institutions. The links are established between UK and overseas universities primarily to enhance research and/or teaching capacity, with the ultimate aim of alleviating poverty and promoting sustainable development. This article draws on data gathered for a large‐scale, multiple‐method evaluation which endorsed the scheme's continuation. It is argued that a crucial factor helping to make individual links a success was good relationships between respective co‐ordinators, although the nature of these relationships varied. The article discusses the extent to which the formation of fruitful academic networks and partnerships enabling knowledge transfer were encouraged. Copyright © 2003 John Wiley & Sons, Ltd.
Governance conditions, roles and capacity‐building needs in the rebel‐held areas of Southern Sudan
Authors: Blunt Peter
Published: April 2003

An assessment is made of the state of sustainable human development (SHD) and the institutions of governance that are in the process of being established in the rebel‐held areas of Southern Sudan. The development roles of the main governance actors—government, civil society and the private sector—are examined and capacity‐building needs are described. The importance of good leadership, institutionalised partnerships between government and national and international NGOs, and capacity building for transparency and accountability is stressed. Most pointedly, the risks of allowing governance practices, suited to the management of a liberation struggle, to spill over into the civil administration of a peaceful state are emphasised. The conditions necessary for the institutionalisation of sound governance practices are discussed. Of particular importance are a genuine desire on the part of the leadership to establish such conditions and a willingness on the part of external donors to address issues of accountability and transparency openly in collaboration with the leadership. The data are also suggestive of broad development strategies that address the bases of SHD and empowerment. These broad strategies are designed to improve the very low levels of health and education that exist in the Southern Sudan, and thereby empower people to engage in economic activity and in governance decision‐making. Rehabilitation and maintenance of the physical infrastructure underlies all development activity. The findings highlight the governance difficulties faced by war‐torn societies, the challenges facing post‐crisis administrations and (confirming Caplan 2002) the need for such administrations to possess sufficient executive authority to be able to perform effectively in situations of ‘pre‐state, post‐imperial chaos’. Most critical of all, however, is the genuine interest of the major powers in doing more than—when it suits them—extinguishing the flames of conflict or establishing acquiescent political regimes following the military pacification of ‘rogue’ or anarchic states. Effective post‐crisis administration and development calls for much greater commitment of resources from the major powers than has been forthcoming to date, reflecting a belief among them that equitable and sustainable global development is the preferred route to the prevention of such crises. Copyright © 2003 John Wiley & Sons, Ltd.
A new approach to the theory of rubberlike elasticity
Authors: Huggins Maurice L.
Published: April 2003

Equations are derived for stress–strain curves for a hypothetical model substance containing a large number of like systems, each assumed to be in equilibrium between two states having different arrangements of the atoms. With this model one can study the dependence of the initial elastic modulus, the limiting strain (for infinite stress), and the over‐all shape of the stress–strain curve on characteristics of the rearranging systems—their number, the initial energy difference between the two states, the shift of atomic positions, etc. Introduction of an assumed proportionality between the shift per rearrangement and the square of the relative length of the sample (in the direction of the shift) leads to stress–strain curves similar to those determined experimentally for natural rubber and other rubberlike materials.
Mechanism of peroxide‐initiated styrene polymerization. Infrared absorption of some polymer samples
Authors: Pfann Harry F. , Williams Van Zandt , Mark H.
Published: April 2003

Previous observations make it probable that one or both ends of a longchain molecule produced by catalyzed vinyl polymerization contain fragments of the initiator. If one uses acid peroxides as initiators, these fragments can contain a carbonyl group. It is the purpose of this paper to investigate whether these carbonyl groups which are present only in a very small amount can be detected by infrared absorption. It seems that in the case of polystyrene initiated with benzoyl peroxide, infrared absorption spectra reveal the presence of a small amount of some carbonyl groups in the polymer. Their amount appears to be in agreement with chemical measurements and with the molecular weight of the material.
Experimental study of copolymerization
Authors: Alfrey T. , Merz E. , Mark H.
Published: April 2003

Using the copolymer composition equation, the critical constants α and β are determined for the systems styrene–2,5‐dichlorostyrene, styrene–methyl acrylate, styrene–diethyl maleate, and styrene–diethyl chloromaleate.
Determination of polymer–liquid interaction by swelling measurements
Authors: Doty Paul , Zable Helen S.
Published: April 2003

The interaction of polymers and liquids can be fairly well characterized by the value of the quantity μ, commonly used in thermodynamics of polymer solutions and usually evaluated from osmotic pressure measurements. The Flory‐Rehner theory of swelling relates the amount of swelling of a slightly cross‐linked polymer in a liquid to μ and a parameter Mc, the average molecular weight between cross links. Mc, may be determined for a cross‐linked polymer from its swelling volume in a solvent in which osmotic pressure measurements with the noncross‐linked polymer have given the value of μ. The cross‐linked polymer, thus calibrated, can be used to obtain the μ value for other liquids by measuring its swelling volume in them. This procedure has been carried out on polyvinyl chloride which can be cross linked by heating. Calibration in three different liquids gave comparable values of Mc, thus checking the Flory‐Rehner theory. The quantity μ was determined at two different temperatures for fifty liquids. The value of μ and its temperature dependence correlate well with the observed properties of the binary systems. Variation of μ with molecular weight in an homologous series is demonstrated.
Density of cellulose fibers. III. Density and refractivity of natural fibers and rayon
Authors: Hermans P. H. , Hermans J. J. , Vermaas D.
Published: April 2003

A micromethod is described for density determinations of artificial cellulose fibers by the floating method, in carbon tetrachloride in a dry and air‐free atmosphere, permitting an accuracy of one part per thousand. The density is derived from the temperature at which the samples neither sink nor float. This temperature varies, with the kind of fiber, between 45° and 65°C. Measurements of the refractive power were carried out simultaneously. The refractivity calculated according to Gladstone and Dale yields slightly lower figures than those found for model fibers in the preceding communication (Part II). The average difference amounts to seven parts per thousand and is ascribed to a systematic error in the density determinations, due to a slight absorption of carbon tetrachloride by the fibers at elevated temperatures. This explanation is supported by experiments. The density of native ramie, of contracted and reoriented ramie, and of several series of rayon fibers spun with increasing stretch, is given. The conclusion is reached that the density is a measure of the percentage of crystalline substances in the fiber and it is shown that there is a correlation between density and sorptive capacity toward water vapor. The percentage of crystalline matter is estimated to be 55–60% in native ramie and 20–25% in rayon.
Preparation and properties of rubberlike high polymers. I. Polymerization of dienes and vinyl compounds in bulk
Authors: Koningsberger C. , Salomon G.
Published: April 2003

The polymerization of dienes under the influence of heat, of diazoaminobenzene, and of benzoyl peroxide, has been studied. Diazoaminobenzene probably acts as a slow, but continuous, source of free radicals giving quantitative yields of methyl rubber of good quality from dimethylbutadiene after a few days to a few weeks at 100–125°C. The effect of diazoaminobenzene on butadiene is the same, but the rate of the uncatalyzed dimerization of butadiene at 100°C. is as fast as that of dimethylbutadiene at 150°C. and, therefore, dimerization interferes much more strongly with the polymerization of butadiene. Only 60% of polybutadiene has been obtained. A few experiments with isoprene showed its position between the two other dienes. The effect of benzoyl peroxide on the polymerization of the dienes appeared to be much smaller than was expected from its known catalytic action on the polymerization of vinyl compounds, e.g., styrene, for in this case its activity is about 100–1000 times greater than that of diazoaminobenzene. It is assumed that a larger number of radicals, produced by the fast decomposition of benzoyl peroxide, causes this difference. Diazoaminobenzene has about the same effect on the polymerization of styrene and acrylonitrile as on that of the dienes. The catalytic effect of benzoyl peroxide on the polymerization of the dienes is, on the contrary, 10,000–100,000 times smaller than on that of the vinyl compounds. This difference can be understood by the assumption that the catalyst is quickly used up by oxidizing the dienes and their polymers. While methyl rubber and the polyisoprene resemble raw natural rubber, polybutadiene, prepared under comparable conditions, is hard, swells moderately, and has a tendency to become brittle as a result of oxidation (aging). Abbreviations used are DAB (= diazoaminobenzene) and BP (= benzoyl peroxide).
Use of a stopcock device for sampling latex
Authors: Medalia A. I.
Published: April 2003

A device is described which permits rapid sampling of systems under pressure.
Modern views on the chemistry of vulcanization changes. III. Reaction of sulfur with squalene and with rubber
Authors: Bloomfield George F.
Published: April 2003

Squalene containing six isoprene units is more free of end‐group effects and less limited in the range of space‐distributional contortions of its carbon chain than mono‐ and diolefins. Hence it is more comparable with rubber than the latter group where matters of chemical reactivity are concerned. Nevertheless, in its reaction with sulfur, squalene pursues a course very similar to that followed by the diisoprene, dihydromyrcene, in that intramolecular sulfide linkages as well as intermolecular polysulfide linkages are formed. Taking into consideration the amount of sulfur which would suffice for the establishment of some given number of the simplest possible intermolecular linkages (i.e., monosulfide linkages), the efficiency of sulfur as a cross‐linking reagent during the vulcanization of squalene is seen to be of a rather low order; this condition might be expected to hold for rubber in the absence of auxiliary mechanisms. So far as can be determined by direct experiment the action of sulfur in forming cross links is not essentially different from that encountered with squalene, since there are indications that both intra‐ and intermolecular sulfide linkages are formed—the latter being of both dialkenyl and dialkyl sulfide type, and, possibly also of alkenyl alkyl type. Under the influence of small amounts of zinc oxide or of various nitrogen‐containing organic accelerators, sulfur reacts with the thiol groups of organic mercaptans forming di‐ and polysulfides, together with hydrogen sulfide. In the presence of rubber the same reaction occurs without actual liberation of hydrogen sulfide and it thus appears that if any thiol groups are formed as intermediates in vulcanization reactions, they will undergo ready conversion into intermolecular di‐ and polysulfide linkages. This may well represent an important auxiliary mechanism of cross linking.
Preparation and properties of rubberlike high polymers. III. Polymerization of mixtures in emulsion
Authors: Salomon G. , Koningsberger C.
Published: April 2003

The copolymerization in emulsion of butadiene with varying amounts of styrene and acrylonitrile and of dimethylbutadiene with the latter vinyl compound has been studied on a laboratory scale. An essential difference between polymeric vinyl compounds and polydienes is the olefinic character of the latter, which leads to typical secondary changes in the polymers originally formed during the completion of the reaction. Such changes are of fundamental importance for the ultimate mechanical properties of polymers and copolymers based on dienes. After a brief discussion of the general theoretical line of thought serving as a base for our experiments, the influence of various factors on the rate of polymerization is pointed out and demonstrated by experiments. The changes in the nitrogen content of copolymers from acrylonitrile and the yields as a function of the reaction time have also been studied. From an investigation of some physical properties, such as solubility and swelling, the existence of true copolymers (of unknown irregularity) has been established. Copolymers from dimethylbutadiene and acrylonitrile represent a new class of olefinic thermoplastics resembling gutta‐percha. Abbreviations used are BP (benzoyl peroxide) and DAB (diazoaminobenzene).
Determination of polystyrene in GR‐S rubber
Authors: Kolthoff I. M. , Lee T. S. , Carr C. W.
Published: April 2003

A convenient procedure for the determination of polystyrene in GR‐S is given. The method depends upon degradation of the GR‐S by tert‐butyl hydroperoxide in the presence of a trace of osmium tetroxide. Polystyrene is not attacked and is separated by precipitation with ethanol.
Polymerization of methyl methacrylate in aqueous emulsions
Authors: Baxendale J. H. , Evans M. G. , Kilham J. K.
Published: April 2003

The kinetics of the polymerization of methyl methacrylate in emulsions has been examined. The initial rate of polymerization is independent of the amount of discontinuous monomer phase present and it is concluded that initiation occurs in the aqueous phase. Monomer is observed to disappear from the discontinuous phase more quickly than it polymerizes, and probably forms a monomer‐polymer mixture with the polymer produced. An increase in the subsequent rate of polymerization is attributed to the fact that propagation of the growing polymer chains occurs in this monomer–polymer mixture and this entails a decrease in the velocity of termination due to the high viscosity of such mixtures.
Investigation of potato proteins
Authors: Jirgensons B.
Published: April 2003

By treating potato juice with acid it was found that potato globulin is converted to albumin and an insoluble casein‐like protein. Potato albumin, salted out with ammonium sulfate and purified by dialysis, is very similar to ovalbumin; it is reconverted into a globulin‐like protein by alkali. Solutions of potato albumin in water, as well as in acids and alkali, have a very low viscosity. Alkaline solutions of globulin have a greater viscosity than those of albumin; the viscosity numbers of the difficulty soluble protein are even greater. On the basis of the viscosity data, it was concluded that the albumin particles are corpuscular, the globulin molecules are longitudinal, and that the dissymetry is greatest for the difficulty soluble protein particles. On the basis of the different solubilities of all three proteins (which apparently have approximately the same chemical composition), it was concluded that the albumin molecule was the smallest and the difficulty soluble protein molecule the largest. An aqueous solution of potato albumin is denatured when heated to 50–60°, the viscosity thereby increasing more than 100‐fold. The solutions become only slightly turbid, but do not flocculate. This unusual viscosity rise can be explained by the transformation of globular albumin molecules into fibrous, elongated particles. Only a slight viscosity increase is observed when alkaline solutions of albumin are heated. Albumin, in the presence of small amounts of salt, is precipitated at 50–60°; the salts also lower the turbidity point. However, very small concentrations of calcium chloride have a stabilizing effect. Albumin is not coagulated at room temperature by 1–2 N salt solutions. The experiments on the effect of cold on potato albumin showed that albumin, after congealing and thawing out, was more easily precipitated than the control solution. The viscosity of the cold‐damaged albumin was somewhat less than that of the control solution. It was ascertained that the deaminated product of potato albumin was very similar to deaminated ovalbumin (solutions of high viscosity; linear colloid).
Heat polymerization of nonconjugated vegetable oils
Authors: Bernstein I. M.
Published: April 2003

A general theory is proposed to account quantitatively for the heat polymerization and gelation of the nonconjugated vegetable oils. This is based on a direct approach to polyfunctionality as developed from quantitative considerations of partial random distribution of the fatty acid components in the triglyceride molecules. The differing polymerization rates of linseed and soybean oils are accounted for on the basis of the assumed influence of certain cis‐trans geometric isomers. The theory accounts for the anomalous extensive linear polymerization and nongelation of olive oil. Calculations from the theory agree substantially with experimental results on average molecular weight, iodine value, and the percentage of insoluble, infusible cross‐linked polymers.
Theory of rolling plastics. II. Thermal effects
Authors: Eley D. D.
Published: April 2003

In the rolling of Plastic sheet the viscous work gives rise to heating of the plastic sheet. The maximum temperature reached in the interior of the sheet during shearing is of the interest, both in the theoretical calculation of roll pressure, and from the point of view of possible thermal decomposition effects. A calculation is given for a simple, some‐what artificial, model, which leads to an upper value for this maximum temperature if a measurement of the average temperature of the emergent sheet is given. The model taken is that of an infinite sheet, of thickness 2δ, in which heat is continuously liberated at the rate of 4ηϕ2 cal. cc. −1 sec. −1, where ϕ is the relevant value of the rate of compression (assumed constant across the sheet). The curve giving the temperature distribution across the sheet is calculated numerically for two cases; it is relatively flat, as would be expected on physical grounds, since the viscosity, η, decreases as the temperature rises. It is concluded that these thermal effects may be neglected in the calculation of roll pressure in Part 1.
Photolysis of rubber
Authors: Bateman L.
Published: April 2003

Rubber hydrocarbon irradiated in vacuo is decomposed by ultraviolet light of wave length less than 4000 Å. The rubber very rapidly becomes insoluble, and liberates a gaseous mixture which consists mainly of hydrogen when the irradiation temperature is less than 150°C. The reaction characteristics have been investigated and point to the occurrence of dissociation processes similar to those deduced for comparable simple olefins. When irradiated above 150°C., small but significant amounts of isoprene appear in the volatile product, thereby providing an experimental means of determining the activation energy for the separation of isoprene from a polyisoprene chain terminated by an allyl radical.
Polyelectrolytes. I. Picrates of 4‐vinylpyridine‐styrene copolymers
Authors: Fuoss Raymond M. , Cathers George I.
Published: April 2003

The conductance in diphenyl ether at 35°C. and 60 cycles of the picrate of a 4‐vinylpyridine‐styrene copolymer (10:90) has been measured. The equivalent conductance, based on the nitrogen content, is of the same order as that of picoline picrate, and varies with concentration in accordance with the law of ion association.
Effect of silver salts on emulsion polymerization systems containing butadiene
Authors: Rainard L. W.
Published: April 2003

The addition of silver nitrate to polymerizable systems containing butadiene can result in increased over‐all rates of conversion. When butadiene is the only monomer and a cationic soap is used the addition of silver nitrate causes* a significant decrease in rate. The most active system studied was one which contained butadiene, styrene, a cationic soap, a peroxide, and silver nitrate. Comparison runs in a GR‐S type formulation with silver nitrate and potassium ferricyanide indicate that the silver salt is the more effective in producing higher over‐all rates of conversion.
Intrinsic viscosities and molecular weights of polyvinyl acetates
Authors: Wagner R. H.
Published: April 2003

A polyvinyl acetate polymer of medium viscosity was fractionated into sixteen fractions (first series) and three of the larger of these further separated into twenty subfractions (second series). The intrinsic viscosities and the osmotic pressure molecular weights were determined at 25°C. and the relation between them was found to be expressed by the equations: first series: [η] = (1.88 × 10−4) M0.69; second series: [η] = (1.76 × 10−4) M0.68. The data indicate that little, if any, increase in homogeneity is to be expected by further successive fractionations and that the equations applicable to the second fractionation series are representative of essentially homogeneous polyvinyl acetates in acetone. An equation applicable to fractionated and unfractionated vinyl acetate polymers is described that is useful in obtaining the intrinsic viscosity from a single viscosity measurement. Several unfractionated materials from different sources were also studied and the calculated ratios of the viscosity‐average to the number‐average molecular weight indicate that the degree of heterogeneity of chain‐length distribution increases with increasing average molecular weight.
Mercaptans as promoters and modifiers in emulsion copolymerization of butadiene and styrene using potassium persulfate as catalyst. III. Calculation of molecular weights and intrinsic viscosities of polymers from mercaptan consumption data
Authors: Harris W. E. , Kolthoff I. M.
Published: April 2003

An empirical equation is described which predicts the intrinsic viscosities of 75:25 butadiene‐styrene emulsion copolymers from data on mercaptan consumption. The form of the equation is as follows:

where [η] is the intrinsic viscosity, P is the conversion, R is the fraction of mercaptan consumed, R0 is the mercaptan charged, and a, b, and c are constants equal to 0.22, 1.12, and 0.66, respectively. Evidence is given that the intrinsic viscosity of mutual‐recipe polymers can be described satisfactorily in terms of mercaptan consumption.
Mercaptans as promoters and modifiers in emulsion copolymerization of butadiene and styrene using potassium persulfate as catalyst. IV. Definition and calculation of modifier efficiency
Authors: Harris W. E. , Kolthoff I. M.
Published: April 2003

The calculation of the “theoretical” minimum modifier requirement, TMMR, for butadiene‐styrene (75:25) copolymers of given intrinsic viscosities at various conversions is described. The TMMR of 75% conversion polymer of intrinsic viscosity 2.0 is R0 = 0.28, which is only about 60% of the value of R0 for commercial primary dodecyl mercaptan (C.M.) in large‐size reactors. The efficiency, E, of a modifier for 75:25 butadiene‐styrene copolymerization using soap as emulsifier and persulfate as catalyst has been defined by and calculated from the equation:

where Mv is the intrinsic viscosity molecular weight of the polymer at conversion, P, with an amount of mercaptan, R0, charged with the monomers. For all modifiers the efficiency is low at low conversions and gradually increases to a maximum with increasing conversion. For different modifiers this maximum may be as at low as 10% conversion or at higher than 80% conversion. After the maximum the efficiency decreases with further increase of conversion. The most efficient modifier for the production of polymers of intrinsic viscosity, [η], at conversion, P, will meet the following conditions, R = 1 at conversion, P, and dP/dR is constant. Inefficient modifiers may be made more efficient by changing the conditions or procedure of polymerization in such a way that the modifier more nearly complies with the above conditions.
Internal plasticization: The effect of chemical structure
Authors: Simril V. L.
Published: April 2003

The elastic and plastic properties of high polymeric materials are functions of the forces holding the molecules together and the ability of small segments of the chains to move about, relative to other segments. Internal plasticization is accomplished by introducing structural features which reduce intermolecular and intramolecular forces and which, in general, decrease the order of the polymer. Physical techniques used to determine the effect of such structural features have been discussed. The results of numerous investigations into the relations between structure and properties have been considered in an attempt to present a simple and consistent physical picture of these relations.
Effect of plasticizers on second‐order transition points of high polymers
Authors: Boyer R. F. , Spencer R. S.
Published: April 2003

This is a review article concerned with the effect of plasticizers on the second‐order transition point and related phenomena in high polymers. The second‐order transition temperature behavior of plasticized polymers can be described by a linear relationship between the square root of the weight fraction of polymer and the reciprocal transition temperature. For certain temperature regions and plasticizer contents, this is mathematically equivalent to the linear decrease of transition temperature with plasticizer content which is also observed experimentally. This latter result is in accord with Zhurkov's theory of the softening action of solvents, which predicts a linear decrease in softening temperature with solvent content, and no dependence on the nature of the solvent. Neither the second‐order transition approach nor Zhurkov's theory permits conclusions about the nature of the plasticizer. However, it is shown empirically that brittle temperature can be represented as a function of the solvent‐polymer interaction constant μ by a curve having a maximum at μ ≈ 0.4. Since μ is also the parameter which measures compatibility, it is seen that the efficiency and the compatibility of a plasticizer are intimately related. Moreover, correlation can be made with older observations showing the relation between efficiency and the temperature coefficient of viscosity of the plasticizer.
Use of perbenzoic acid in analysis of unsaturated compounds. I. Preparation and stability of solutions of perbenzoic acid
Authors: Kolthoff I. M. , Lee Thomas S. , Mairs Mary Anne
Published: April 2003

The preparation of perbenzoic acid has been investigated in a n attempt to obtain standard solutions of perbenzoic acid suitable for the amlyszk of unsaturated compounds. Some modifiations of the procedure given by Braun for the preparation of a solution of perbenzoic acid in a n organic solvent are recommended. A study has been made of the stability of solutions of perbenzoic acid in chloroform and in benzene. Benzene or benzene‐chloroform mixtures are recommended as solvents for perbenzoic acid. Chloroform solutions of perbenzoic acid which do not contain inhibitors for decomposition have been found to be definitely undesirable in analytical work because perbenzoic acid catalyzes the decomposition of chloroform by oxygen. construction Finance Corporation, in connection with the Government Synthetic Rubber Program.
Polyisoprenes: A theory of the formation of terpenes and related compounds
Authors: Tobolsky Arthur V. , Castro Luis , Stein Sidney J. , Sacher Alex
Published: April 2003

A mechanism is presented which shows how terpenes and related compounds, some of which are found associated with trans—polyisoprene in nature, may be expected to be formed by a radical chain oxidative degradation of trans—polyisoprene.
Reaction of tetrachlorophthalic anhydride with cellulose derivatives
Authors: Utermohlen William P. , Wallace E. Louise
Published: April 2003

Tetrachlorophthalic anhydride (TCPA) was reacted with cellulose diacetate and with cellulose diethyl ether in dioxane solution to produce esters with rather low tetrachlorophthalyl contents. Phthalic anhydride was found to be considerably more reactive than was TCPA with these cellulose derivatives, especially if pyridine was used as the reaction solvent. Acylations could not be executed with TCPA in the presence of pyridine as solvent, however, because this material decomposed the anhydride, removing chlorine from it. The TCPA derivatives were more limited in solubility than were the corresponding esters made from phthalic anhydride.
Diffusion of water into a polymer
Authors: Custers J. F. H.
Published: April 2003

In contradistinction to the usual methods, the diffusion of water into a polymer has been investigated by starting from a disk of the material surrounded by water. In this way, actual service conditions are often closely approached. Since a theoretical basis is desirable, equations are given for this type of diffusion, and experiments with a wood flour containing phenol‐formaldehyde material were performed from which values for the permeation constant could be derived.
Anisotropic diffusion of direct dyes in fibers
Authors: Frey‐Wyssling A.
Published: April 2003

It is shown that molecules of benzidine dyes can diffuse into cellulose fibers only perpendicular, not parallel, to the fiber axis.
Influence of structure on polymer‐liquid interaction. I. Relative and absolute values of swelling equilibria
Authors: Salomon G. , Van Amerongen G. J.
Published: April 2003

The swelling of vulcanized natural rubber, Buna S, neoprene, Perbunan, and Perbunan Extra was measured in various organic liquids. The essential influence of polarizability and polarity on the swelling equilibrium is illustrated by comparing series of solvents and polymers with gradually changing geometrical and chemical structure. Experiments on the influence of temperature and of strain on the swelling equilibrium are reported. The swelling properties of ebonites and similar derivatives allow some conclusions on the amount of cross linking in these polymers.
Course of acetylation and deacetylation reactions of cellulose fibers. II. X‐ray diagrams
Authors: Vermaas D. , Hermans P. H. , Weidinger A.
Published: April 2003

A discussion is offered of the x‐ray patterns of partially acetylated and saponified cellulose model filaments with varying acetyl contents. They are substantially in conformity with the swelling experiments previously described in Part I (page 397) of this paper. (1) In nonrecrystallized filaments, chemical reaction takes place in the crystallites and the intercrystalline regions from the very beginning of the experiment. The rate of chemical conversion, however, is larger in the latter. (2) Acetylation of the hydrate cellulose crystallites results in a gradual increase in the (101) spacing, A0; the A3 and A4 reflections [corresponding to (101) and (002), respectively] remain unimpaired up to a gross acetyl content of at least 1.5 acetyl groups per glucose residue. (3) Maximally acetylated filaments containing 2.3 acetyl groups per glucose residue may be recrystallized by heating in methanol or ethanol. The diagram of the recrystallized product is identical with the pattern of cellulose triacetate II. With about halfway acetylated or saponified products, recrystallization is not realizable by means of a heating process in water or methanol. (4) Enhanced degree of local order as the result of previous recrystallization of maximally acetylated products produces a more pronounced difference in rate of saponification between the “crystalline” and “amorphous” fiber portions.
Multi‐ingredient polyamides
Authors: Catlin W. E. , Czerwin E. P. , Wiley R. H.
Published: April 2003

Multi‐ingredient polymeric amides have been prepared by the condensation, under amide‐forming conditions of various combinations and ratios of components comprising hexamethylenediammonium adipate, hexamethylenediammonium sebacate, and ϵ‐aminocaproic acid or ϵ‐caprolactam. The physical properties of the investigated linear polymeric amides range, depending upon the polymer components and the proportions employed, from high‐softening, stiff, and difficulty soluble compositions to relatively low‐softening, pliable, and easily soluble polymers.
Tensile strengths of pure gum natural rubber compounds
Authors: Gee Geoffrey
Published: April 2003

The tensile properties of a range of pure gum natural rubbers has been reviewed, and it has been shown that their principal features can be understood on the assumption that the tensile strength measured in a given test depends directly on the amount of crystallization at break. The most important single factor in determining tensile strength is the degree of cross linking. Cross linking is only needed in order to prevent plastic flow, thus permitting the molecules to be aligned by stretching, and hence to crystallize. A very highly cross‐linked rubber is weak because the load required to stretch it is so high, that the rubber is broken before the elongation becomes large enough to produce crystallization. In general, vulcanization also involves reactions, e.g., the combination of sulfur with the rubber, which inhibit crystallization by producing structural modifications of the rubber. These reduce the tensile strength, especially when the degree of cross linking is large. These ideas readily explain the effects of swelling and of the temperature of test. They are also used in a brief discussion of the phenomena of overcure, reversion, and aging.
Emulsion polymerization at high temperature
Authors: Rabjohn Norman , Dearborn R. J. , Blackburn W. E. , Inskeep G. E. , Snyder H. R. , Marvel C. S.
Published: April 2003

The emulsion polymerizations of butadiene and styrene and of butadiene alone have been studied at temperature of 90–160°. The effects of changes in catalysts, modifiers, times of polymerization, and other variables have been investigated. The rate of polymerization at 110° is markedly increased over that at 50° and the final product is a less modified and less processable polymer. However, the standard evaluation and road tests indicate this polymer may be a useful one.