bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reproductive success: Which meaning?
Authors: Crognier E. 
Published: April 2003

AbstractThe theory of kin selection (the part played by behavior in the changes of mean inclusive fitness) induced many human sociobiologists to think that since behavior was involved in the increase in fitness, this last entity could apply to the individual. Approximated by the individual's lifetime reproductive success, this measure became the keyword of studies linking social and cultural behavior to biological adaptive processes. To be commonly applicable to human populations, it had to be simplified to represent the number of offspring reaching sexual maturity and most existing studies are based on this definition. The current trend, however, seems to consider that, like inbreeding, reproductive success takes its signification in the depth of successive generations. These diverse measures were tested in two traditional populations, Berber and Aymara, and show that finding a satisfactory evaluation of reproductive success is a problem that is still far from a solution. Am. J. Hum. Biol. 15:352–360, 2003. © 2003 Wiley‐Liss, Inc.
Identifying cumulative trauma disorders of the upper extremity in workers' compensation databases
Authors: Zakaria Dianne , Mustard Cam , Robertson James , MacDermid Joy C. , Hartford Kathleen , Clarke Judy , Koval John 
Published: April 2003

AbstractBackgroundImpeding the use of workers' compensation databases for surveillance of cumulative trauma disorder of the upper extremity (CTDUE) is the lack of valid and reliable extraction strategies.MethodsUsing the Z795‐96 Coding of Work Injury or Disease Information standard, analgorithm was developed to classify claims as definite, possible, or non‐CTDUE. Reliability was assessed with standardized claim reviews.ResultsModerate to substantial agreement (Kappa = 0.48, 95% CI 0.42–0.54, n = 328; weighted Kappa = 0.75, 95% CI 0.70–0.80, n = 328) was demonstrated. The algorithm produced relatively homogeneous groups of definite and non‐CTDUE claims but 29.1% of the possible CTDUE claims were categorized as definite CTDUE by claim review. Part of body agreement was almost perfect (Kappa = 0.81–1.00) when determining whether the upper extremity or specific parts of the upper extremity were involved.ConclusionsThe algorithm can be used to estimate the number of CTDUE and extract homogeneous groups of definite and non‐CTDUE claims. Furthermore, certain upper extremity part of body codes can be used to target anatomically defined claims. Am. J. Ind. Med. 43:507–518, 2003. © 2003 Wiley‐Liss, Inc.
The properties of polyvinyl fluoride film
Authors: Simril V. L. , Curry Barbara A. 
Published: April 2003

AbstractPolyvinyl fluoride can be made into clear and pigmented films in thickness ranging from 0.0005 to 0.004 in. and in both biaxially oriented and essentially unoriented forms. These films are extremely long‐lived outdoors and are strong, tough, flexible, and inert. Useful lives of 10 years and more in Florida exposure have been demonstrated, and it has been shown that there is a linear relation between exposure time and the logarithm of film extensibility in both natural and accelerated weathering. Biaxial orientation of PVF film results in high tensile and impact strength and great resistance to flexural fatigue. Lesser degrees of orientation result in higher tear strength, greater extensibility at higher temperatures, and decreased shrinkage at high temperatures. Both oriented and unoriented films retain a large proportion of their strength properties after 1500 hr. in steam or in 150°C. dry heat. Both are highly resistant to nonoxidizing acids, bases, and solvents. PVF films have high dielectric constants, good dielectric strength, and intermediate electrical resistivity and dissipation factor.
Methyl α‐cyanoacrylate. I. Free‐radical homopolymerization
Authors: Canale A. J. , Goode W. E. , Kinsinger J. B. , Panchak J. R. , Kelso R. L. , Graham R. K. 
Published: April 2003

AbstractMethyl α‐cyanoacrylate, when suitably inhibited by Lewis acids against anionic polymerization, can be polymerized readily with free‐radical initiators to form hard, clear, high molecular weight polymers. The ratio of kp2/kt is approximately 0.021 at 60°C. if 100% efficiency of initiation by azobisisobutyronitrile is assumed. Acceleration occurs at very low conversion to polymer during bulk polymerizations. The homopolymer is thermally unstable at temperatures only slightly above the glass temperature (estimated to be 165–170°C.). Degradation of the polymer under gamma irradiation is pronounced, only 18 e.v. being required per main‐chain scission.
Crystallinity of siloxane polymers
Authors: Fischer David J. 
Published: April 2003

AbstractFour homopolymers (dimethyl‐, phenylmethyl‐, diphenyl‐, and trifluoropropylmethylpolysiloxanes) and two copolymer systems (dimethylsiloxane–phenylmethylsiloxane and phenylmethylsiloxane–diphenylsiloxane) have been studied by observing spherulite nucleation, growth, and melting. A characteristic crystallization temperature is proposed which can be considered representative of the equilibrium freezing–melting point. This work isolates the crystallinity characteristics of pure siloxane polymer and copolymer systems.
Stress‐strain testing of rubbers at high rates of elongation
Authors: Dannis Mark L. 
Published: April 2003

AbstractA high speed stress‐strain apparatus has been constructed to measure the strength and elongation of rubbery materials at extension rates roughly 250 and 550 in./sec. The test sample is stretched by falling weight which catches a protruding lug on the lower jaw of the sample. The weight falls from a magnetic grip at one of two selected stations. The potential energy of the falling weight is large compared to the energy under the stress‐strain curve in order to avoid appreciable slowing of the weight during the period of stretch. The excess energy is dissipated in several kinds of damping mechanisms without damage to other than expendable crash pads. The tensile load on the rubber sample is carried by a stiff‐strain‐gage beam, the output of which is displayed on an oscilloscope for photographic recording. Stress‐strain curves of rubber recorded for stretch rates about 550 in./sec. show evidence of sonic wave pulses in the early portions of the extension cycle. Ultimate tensile and elongation values differ somewhat from values obtained using conventional test machines.
Flexural fatigue testing of polyesters
Authors: Hagerup E. 
Published: April 2003

AbstractA method is described for evaluating flexural fatigue properties of unsaturated polyesters. With the use of the Sonntag fatigue machine and a modified version of the Prot principle, dynamic parameters and fatigue properties can be readily determined. Testing of castings with no reinforcement reveals two different modes of resin fracture, brittle and plastic. A plastic fracture implies that the resin yields before breaking. Reproducibility of the results is directly related to the type of fracture, ranging from very good for a plastic resin to very poor for a brittle. Close proximity of yield points and endurance limits for plastic resins confirms validity of Prot's method of extrapolating the latter parameter. Incorporation of two layers of glass cloth in positions corresponding to the outermost plies in a laminate shows that failure at the glass–resin interface may be the overriding cause of laminate breakdown. Both plastic and brittle resins become stiffer in the presence of glass, but only the plastic resin is realizing its inherent strength to give a stronger reinforced casting. The brittle resin is, on the other hand, weaker with glass present because of inability to dissipate local stress concentrations at the warpfilling crossovers. The break amplitude is a particularly significant parameter because it is expected to be the same in a normal laminate as in these castings with only the outermost plies present. Additional plies would merely increase stiffness and, correspondingly, the stress to reach amplitude coincident with failure at the outermost plies. Use of relatively thick test bars (0.5 in.) permits insertion of a thermocouple in the neutral plane without affecting dynamic properties. Measurement of the temperature rise during flexing allows assessment of the damping capacity of the glass–resin system, which is of particular importance for resonance fatigue. By this means, three different types of glass–resin systems could be distinguished: (1) weak and high damping (plastic), (2) strong and low damping (brittle), (3) strong and high damping (tough). For a particular resin, the behavior is determined by the basic composition as well as by degree of cure. For well‐cured polyester samples, several links were found between dynamic parameters, such as stiffness, fatigue strength and damping, and basic composition. Distance between crosslinks in the polyester backbone thus appears to have a direct bearing on strength and damping. Such relationships are valuable in that they make possible predictions of the fatigue behavior of a given polyester formulation.
Infrared spectra of stereoregular polymethyl methacrylate
Authors: Nagai H. 
Published: April 2003

AbstractStereospecific polymerization of deuterated methyl methacrylates, CH2C(CH3)‐COOCD3, CD2C(CD3)COOCH3, and CD2C(CD3)COOCD3, which were prepared by the acetone–cyanohydrin method, were carried out. From the polarized infrared study of polymethyl methacrylate and its deuterated analogue, the spectra of stereo‐regular polymethyl methacrylates were tentatively assigned in the 4000–400 cm.−1 region. The isotactic polymers are easily crystallized and show intensity variations of bands. These bands originate mainly from the deformation vibrations of the α‐CH3 group, the stretching vibrations of the CCO side chain, and the skeletal stretching vibration coupled with CH2 rocking vibration.
Diffusion of gases in fluorocarbon polymers
Authors: Brandt W. W. , Anysas G. A. 
Published: April 2003

AbstractThe diffusion and solubility coefficients and their temperature coefficients of several gases in fluorocarbon polymers were measured by a spring balance and radiotracer method. The activation energies of small molecule diffusion in polytetrafluoroethylene increase with the diffusate molecular diameter squared. The increase is less than that found in many other typical polymers and this is probably due to pre‐existing holes or channels. The latter are most likely to occur in polymers consisting of stiff chain molecules which have a low packing efficiency. Furthermore, the activation energies are not simply proportional to the cohesive energy density. These findings and the general relation between activation energy and solute molecular size can be explained in terms of the model proposed earlier. The apparent frequency factors in the Arrhenius expression for the diffusion coefficients also are low in comparison to other typical polymers presumably because the diffusate molecules are forced to follow a tortuous path through the polymer. The effect of polymer crystallinity and transitions are discussed briefly. Many molecular motions apparently lead to successful diffusion events, again in agreement with the model mentioned above. A simple and rather unambiguous method to derive activation entropies is reported and the diffusion processes in low and high molecular weight materials have been compared.
Redispersible latex polymer
Authors: Guziak L. F. , Maclay W. N. 
Published: April 2003

AbstractLatices containing 55 parts of styrene, (45 − X) parts of 2‐ethylhexyl acrylate, and X parts of methacrylic acid, where X > 15, have been shown to yield discontinuous crazed films upon drying. These clear transparent polymer granules upon immersion in water containing a base are peptized to form a reconstituted latex containing spherical particles of the same size as the original latex particles. Inclusion of small amounts of a filming aid in the original or reconstituted latex permits the deposition of continuous polymer films which are rendered water‐resistant by baking. The property of redispersibility in water of transparent flakes of polymer is attributed to limited particle coalescence in the polymer grit. The incorporation of relatively high levels of carboxyl groups in the polymer is essential to the redispersion of the polymer by dilute solutions of base. Ionization of the carboxyl groups on the particle surfaces upon addition of a base gives rise to the sudden development of repulsive Coulombic forces which cause particle separation, after which surface forces are sufficient to restore the semiplastic particles to their original spherical shape. Inability to redisperse the film a second time may be due to polymer plasticization or to the migration of carboxyl groups to the particle interior as a result of coalescence forces.
Dynamic mechanical properties of supported polymers. II. Application of the torsional braid technique to the study of the curing and stability of resins
Authors: Gillham John K. , Lewis Armand F. 
Published: April 2003

AbstractTransformations, physical and chemical, which occur in polymeric systems are usually accompanied by changes in rigidity. In the present method, a modified torsional pendulum is employed such that the vertical specimen shaft consists of a fabric braid which is impregnated with the polymeric material under investigation. Therefore, in principle, any changes in the mechanical properties of the composite will be reflected by changes in frequency of free oscillation of the system. This dynamic mechanical technique provides a very sensitive tool for following nondestructively, the liquid to solid transitions accompanying the curing of polymers. In this communication the utility of the torsional braid technique in the study of heat resistant polymers is emphasized. Curing and thermal softening behavior, as well as pyrolytic and oxidative degradations are monitored with precision. A comparative study between three thermosetting resins, i.e., a phenolic, an unsaturated polyester and a phosphonitrilic, is presented.
Dynamic testing of elastomer mountings
Authors: Cardillo R. M. 
Published: April 2003

AbstractElastomer mountings are used extensively for impact and shock absorption and for the control of noise and vibration. Dynamic testing has become increasingly important in the formulation, design and evaluation of effective mount materials. A servocontrolled hydraulic tester has been used for the forced vibration testing of various elastomer compounds. The essential dynamic properties of such materials can be obtained directly over a broad range of operating conditions. Frequency, amplitude, and preload can be independently controlled and different test temperatures can be obtained through the use of an insulated control chamber. A production type automotive engine mount was used for most of the tests. Experimental compounds were molded into test mounts and checked for dynamic spring rate and coefficient of damping. The effect of different operating conditions such as frequency, amplitude, preload, and temperature on the dynamic properties of butyl mounts is described. Data are also presented on the role of compounding in altering the properties of mounts. Some data are also presented on the characteristics of natural rubber, SBR, and EPR mounts. The dynamic properties of the mount determine its performance features in a mounting system. The transmission of forces in a simple mounting system can be calculated using dynamic property data and the appropriate transmissibility equation. This has been done for several of the mounts tested and the vibration isolation characteristics of each are discussed. The data illustrate the effect of mount properties on transmissibility.
Memory effects in irradiated polyethylene
Authors: Odian George , Bernstein Bruce S. 
Published: April 2003

AbstractThe memory of irradiated polyethylene has been studied with emphasis on the magnitude of the restoration force exerted by the deformed polymer during the process of restoration to the nonstressed state and on the degree of completeness with which restoration occurs. The particular form of the memory effect studied has involved the deformation of the heated polymer followed by “locking‐in” of the memory via cooling. Subsequent heating restores the deformed specimen to the undeformed state. The memory effect has been studied under both nontransparency (NT) and transparency (T) deformation conditions. The effects of parameters such as the polymer properties (Tm, density, molecular weight), radiation dose, and deformation and restoration conditions on the degree of restoration and restoration force have been investigated. The results of this study may be summarized as follows. Restoration temperatures equal to or above the crystalline melting point (Tm) of the polymer are required in order to obtain complete restoration. The restoration temperature increases with increasing polymer crystalline melting point. The degree of restoration increases with increasing restoration temperature for NT deformed specimens. T deformed specimens do not begin to restore until the temperature approaches the Tm of the polymer. The restoring force increases with decreasing deformation temperature. NT deformation results in larger restoring forces and faster restoration relative to T deformation. The restoring force increases with increasing radiation dose for both T and NT deformations, the effect being greater for NT deformation. Radiation dose, however, above a minimum value does not affect the degree of restoration. The restoring force increases with increasing polymer initial molecular weight for T deformation.
Self‐extinguishing polystyrene foaming‐in‐place beads
Authors: Jahn A. K. , Vanderhoff J. W. 
Published: April 2003

AbstractThe preparation of practical self‐extinguishing polystyrene foaming‐in‐place compositions by suspension polymerization is described. The halogen necessary for self‐extinguishing characteristics is incorporated by chain transfer. The synergistic effect of organic peroxides decreases drastically the amount of halogen necessary. For example, 0.3 pph 1,2‐dibromotetrachloroethane in the presence of 0.2 pph dicumyl peroxide renders the composition self‐extinguishing, while 1.0 pph is necessary without peroxide. The rate of polymerization is unaffected by the presence of this chain transfer agent, while the molecular weight is reduced considerably. The effectiveness of other halogenated chain transfer agents and peroxy compounds has been demonstrated. Silicone mold release agent exerts a deleterious effect on the self‐extinguishing properties.
Behavior of cis‐polybutadiene during mastication
Authors: Kraus Gerard , Rollmann K. W. 
Published: April 2003

AbstractCold mastication of natural rubber in presence of oxygen leads to scission by a shear mechanism with subsequent stabilization of the free radicals by oxygen, while at high temperatures oxidative scission becomes the dominant mechanism. Studies of the behavior of cis‐polybutadiene reveal that similar reactions are effective, but occur at much reduced rates. Shear degradation is particularly difficult to achieve in typical cis‐polybutadienes. This is related to the molecular weight distribution of these polymers which usually lack the very high molecular species most subject to shear‐induced degradation, in agreement with the theory of F. Bueche. It is shown that when such a high molecular weight fraction is supplied, shear breakdown may be realized. All cis‐polybutadienes undergo oxidative breakdown at high temperatures, the scission rate becoming appreciable above 140°C. A number of oxidation catalysts have been found which markedly increase the scission rate without leading to a correspondingly large increase in crosslinking. Significant improvements in processing may be realized in this manner.
Determination of polyolefin film properties from refractive index measurements
Authors: Schael George W. 
Published: April 2003

AbstractA technique is described for determining the density of polyolefin film from refractive index measurements. The procedure involves the measurement of the refractive indexes (nx, ny, and nz) along the three major axes of a film sample and conversion of the arithmetic average refractive index to a density value. The refractive index data are also used to calculate the per cent crystallinity and birefringence in the film.
Properties of semicrystalline polyolefins: Poly‐4‐methyl‐1‐pentene
Authors: Isaacson R. B. , Kirshenbaum I. , Feist W. C. 
Published: April 2003

AbstractA study has been carried out of the thermodynamic properties, physical and mechanical properties, and crystallization behavior of poly‐4‐methyl‐1‐pentene (poly‐4‐MP). Data were obtained for the heat and entropy of fusion. Poly‐4‐MP is characterized by a comparatively high tensile strength, stiffness, and surface hardness. The impact is low at room temperature. The adverse effect of temperature on tensile strength, creep, and other polymer properties is greater for poly‐4‐MP than for polypropylene. Poly‐4‐MP is highly transparent, probably due to limited spherulite growth. Spherulitic growth was promoted through copolymerization with propylene by a technique of sequential monomer addition. The resultant product had an increased crystalline melting point (244 vs. 238°C. for the poly‐4‐MP homopolymer). The significance of these results and the effect of temperature on the birefringence of poly‐4‐MP are discussed.
Extracellular polysaccharide produced from glucose by Arthrobacter viscosus NRRL B‐1973: Chemical and physical characterization
Authors: Jeanes Allene , Knutson C. A. , Pittsley J. E. , Watson P. R. 
Published: April 2003

AbstractThe polysaccharide produced in good yields by Arthrobacter viscosus NRRL B‐1973 when grown in liquid medium containing glucose has been isolated from the culture fluids, purified and characterized. The constituents of this water‐soluble polysaccharide have been shown to be D‐glucose, D‐galactose, and D‐mannuronic acid (as the potassium salt) in approximately equimolar proportions, and about 25% of O‐acetyl groups. The rarity of known occurrences of D‐mannuronic acid in polysaccharides other than alginates is documented. Properties which have been observed as significant for utilization include, for both native and deacetylated forms of the polysaccharide: high viscosity of dispersions in water and in solutions containing chlorides, stability of viscosity to shear and to pH change in the normal range, and excellent quality of unsupported films; and for the native polysaccharide: stability in storage and the favorable influence of alcohol‐water solvent on rate of dispersion and viscosity attained.