bluuebunny/crossref_metadata_2025_split huggingface dataset:
Why do cotton‐top tamarin female helpers carry infants? A preliminary study
Authors: Sánchez Susana , Peláez Fernando , Gil‐Bürmann Carlos 
Published: August 2002

AbstractShortly after giving birth, cotton‐top tamarin mothers frequently attack the eldest female helpers [Snowdon et al., American Journal of Primatology 31:11–21, 1993]. Sometimes this aggression leads to the eviction of the eldest daughters from their natal groups 3–4 months after the birth of infants [Price & McGrew, Folia Primatologica 57:16–27, 1991]. We propose that daughters, during the act of carrying infants, may receive less aggression from mothers than when they are not carrying. On the other hand, given that mothers benefit from having others carry their infants, overall aggression received by female helpers from their mothers might be lower in those female helpers with a larger relative contribution to this activity. Four groups were observed during the first 9 weeks following the birth of infants, and aggression received was recorded for symmetrical as well as nonsymmetrical interactions. We found a positive correlation between contribution to infant carrying of female helpers and the overall aggression received from their mothers. Furthermore, the two eldest daughters with highest values of carrying contribution were evicted from their natal groups 3–4 months after the birth of infants. Although mothers do not appear to be more tolerant of female helpers that contribute the most to infant carrying, daughters do benefit from reduced aggression during the act of carrying, and remain in their natal group during the time period when infants must be carried. Am. J. Primatol. 57:43–49, 2002. © 2002 Wiley‐Liss, Inc.
Niche separation in Varecia variegata rubra and Eulemur fulvus albifrons: II. Intraspecific patterns
Authors: Vasey Natalie 
Published: August 2002

AbstractBased on a year‐long field study in northeastern Madagascar, I summarize annual patterns of niche use (food patch size, diet, forest height, and forest site) in two sympatric lemurs, Varecia variegata rubra and Eulemur fulvus albifrons. Furthermore, I examine intraspecific patterns of niche use according to sex, season, and reproductive stage in these two lemurs that differ in terms of energetic investment in reproduction. Lemurs as a group provide a special opportunity to test hypotheses concerning sex differences in niche use. Due to their body size monomorphism and seasonal, synchronous pattern of breeding, it is possible to directly evaluate whether sex differences in diet reflect high energetic investment in reproduction by females. Results confirm the hypothesis that intraspecific variation in niche use (e.g., sex differences, seasonal differences) would be more pronounced in V. v. rubra than in E. f. albifrons, due in large measure to the former's relatively high energetic investment in reproduction: 1a) Dietary sex differences in V. v. rubra are most pronounced during costly reproductive stages and involve acquisition of low‐fiber, high‐protein plant foods. Females of both species consume more seasonally available low‐fiber protein (young leaves, flowers) relative to conspecific males during the hot dry season, but only in V. v. rubra females is this pattern also evident during gestation and lactation. 1b) The diets of female V. v. rubra and female E. f. albifrons are more similar to each other than are the diets of conspecific males and females in the case of V. v. rubra. This is not uniformly the case for female E. f. albifrons. This finding confirms a hypothesis put forward in Vasey ([2000] Am J Phys Anthropol 112:411–431) that energetic requirements of reproductive females drive niche separation more than do the energetic requirements of males. 1c) Both species synchronize most or all of lactation with seasonal food abundance and diversity. E. f. albifrons shows a more protracted period of synchrony, and this may contribute to its wide biogeographic distribution in Madagascar. 2) Sex differences and seasonal differences in microhabitat use reflect intraspecific patterns of thermoregulation, predator avoidance, and in the case of V. v. rubra, reproduction. One important factor selecting for body size monomorphism in lemurs appears to be the tight synchrony between lactation and periods of food abundance afforded by annual, seasonal breeding. Am J Phys Anthropol 118:169–183, 2002. © 2002 Wiley‐Liss, Inc.
Orthogonal factor coefficient development of subcutaneous adipose tissue topography (SAT‐Top) in girls and boys
Authors: Tafeit Erwin , Möller Reinhard , Sudi Karl , Horejsi Renate , Berg Aloys , Reibnegger Gilbert 
Published: August 2002

AbstractThe new optical device Lipometer allows noninvasive, quick, and safe determination of the thickness of subcutaneous adipose tissue (SAT) layers (in mm) at any site of the human body. The specification of 15 evenly distributed body sites enables the precise measurement of subcutaneous body fat distribution, so‐called subcutaneous adipose tissue topography (SAT‐Top). SAT‐Top was measured in 980 children aged 7–19 years. In this paper we describe the degree to which SAT‐Top body sites are intercorrelated. We consider whether a meaningful reduction of data is possible using factor analysis, which factors can be extracted, and how SAT‐Top data of children can be added to a factor value plot, depicting the essential results of age‐dependent subcutaneous fat development.SAT layers situated on the same body area provide correlation coefficients up to +r = 0.91. Two factors are extracted: factor 1, containing all upper body sites (from neck to hip); and factor 2, consisting of all leg body sites.When all 980 children are divided into three age groups in a factor value plot, the first age group (7–11 years) shows almost equal SAT‐Top development in boys and girls. Afterwards, for the consecutive age groups 2 (11–15 years) and 3 (15–19 years), the age‐dependent subcutaneous fat development of boys and girls progresses into nearly orthogonal directions. Am J Phys Anthropol 115:57–61, 2001. © 2001 Wiley‐Liss, Inc.
Relative variation in human proximal and distal limb segment lengths
Authors: Holliday Trenton W. , Ruff Christopher B. 
Published: August 2002

AbstractThe pattern of variation and covariation of proximal and distal limb segment lengths was examined within and between 20 geographically diverse skeletal samples of modern humans. Analyses of variance‐covariance matrices (VCMs) of logarithmically transformed (ln) variates of humerus, radius, femur, and tibia length were performed to test the following hypotheses: first, within populations, the distal and proximal segments will have equal relative (i.e., size‐independent) variability. However, between populations, the tibia is predicted to be more variable than the other segments. Tests of fit of computed VCMs to theoretical matrices by an iterative procedure (Anderson [1973] Ann. Stat. 1:135–141) reject the equal variance hypotheses, rather suggesting that the relative variances of the distal limb segments are greater than are those of the proximal. Males and females differ somewhat in that within females, the distal segments of both limbs have equal variance, while within males, the tibia has greater relative variance than the radius. The second hypothesis, regarding between‐group variability, is somewhat supported in that between human populations, one cannot reject that the tibia has greater relative variance than the other limb segments. However, neither can one reject an alternative hypothesis that both distal limb segments (tibia and radius) are more variable than the proximal segments. Differential growth allometry is explored, and likely plays a major role in differences seen both within and between human populations. Am J Phys Anthropol 116:26–33, 2001. © 2001 Wiley‐Liss, Inc.
In vitro effects of tributyltin on functional responses of haemocytes in the clam Tapes philippinarum
Authors: Matozzo Valerio , Ballarin Loriano , Marin Maria Gabriella 
Published: August 2002

AbstractThe effects of tributyltin (TBT, as the chloride) on circulating cells from the clam Tapes philippinarum were investigated, in order to set up quick and reproducible in vitro bioassays to evaluate TBT toxicity in bivalve molluscs. Haemocytes, collected from the adductor muscle of clams, were exposed for 60 min at 25 °C to sublethal concentrations of TBT (0.01, 0.05, 0.1 µM) and the effects on uptake of the vital dye Neutral Red, and both superoxide dismutase (antioxidant enzyme) and lysozyme (bacteriolytic enzyme) activities were spectrophotometrically evaluated. Exposure of haemocytes to 0.05 µM TBT caused a significant increase (P < 0.05) in Neutral Red dye uptake compared with controls, whereas no differences resulted after exposure to 0.01 and 0.1 µM TBT. Enlarged lysosomes were observed in haemocytes exposed to 0.05 µM TBT. Moreover, in haemocytes treated with 0.05 µM and 0.1 µM TBT, superoxide dismutase activity significantly decreased (P < 0.05 and P < 0.01 respectively) with respect to that of controls. A significant decrease in lysozyme activity was also observed in haemocytes exposed to 0.05 (P < 0.01) and 0.1 µM TBT (P < 0.001). These results suggest a relationship between TBT exposure and alterations in functional responses of haemocytes in T. philippinarum. The proposed assays are sensitive, rapid and reproducible. They may be proposed as biomarkers, although their responsiveness needs to be more fully evaluated in haemocytes collected after clam exposure in both laboratory and field conditions. Copyright © 2002 John Wiley & Sons, Ltd.
Mechanical properties, oil resistance, and thermal aging properties in chlorinated polyethylene/natural rubber blends
Authors: Sirisinha Chakrit , Sae‐Oui Pongdhorn , Guaysomboon Jantagarn 
Published: August 2002

AbstractThe use of natural rubber (NR) for partly substituting elastomeric chlorinated polyethylene (CPE) was determined. Mechanical and thermal aging properties as well as oil resistance of the blends were also investigated. The amount of NR in blends significantly affected the properties of the blends. The blends with NR content up to 50 wt % possessed similar tensile strength to that of pure CPE even after oil immersion or thermal aging. Modulus and hardness of the blends appeared to decrease progressively with increasing NR content. These properties also decreased in blends after thermal aging. After oil immersion, hardness decreased significantly for the blends with high NR content, whereas no change in modulus was observed. The dynamic mechanical properties were determined by dynamic mechanical thermal analysis. NR and CPE showed damping peaks at about −40 and 4 °c, respectively; these values correlate with the glass‐transition temperatures (Tg) of NR and CPE, respectively. The shift in the Tg values was observed after blending, suggesting an interfacial interaction between the two phases probably caused by the co‐vulcanization in CPE/NR blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 22–28, 2002; DOI 10.1002/app.10171
Polymerization and characterization of acrylonitrile with γ‐methacryloxypropyltrimethoxy‐silane grafted bentonite clay
Authors: Seçki̇n Turgay , Gültek Ahmet , i̇çduygu M. Galip , önal Yunus 
Published: August 2002

AbstractNovel natural clay–polymer hybrid materials are prepared from natural bentonite that was modified with silane‐coupling agent, γ‐methacryloxypropyltrimethoxysilane (A‐174), and acrylonitrile. By changing the molar ratio of acrylonitrile in the initial monomer feed, several clay–hybrid materials were prepared. The structure and thermal stability of hybrid materials were investigated by various methods. The A‐174‐modified bentonite was dispersed in a solution of acrylonitrile in toluene. In this system, radical polymerization in the presence of AIBN was carried out. Product formed at the particle surface was either physically bound by entanglement or chemically bound by covalent bonding to the silane. In this way, core–shell morphology was obtained with an inorganic core and a polymer shell. The results showed that bonding at the surface of bentonite took place by hydrolytic cleavage of methoxy groups of A‐174 with hydroxy groups of bentonite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 164–171, 2002; DOI 10.1002/app.10289
Development and characterization of magnetorheological polymer gels
Authors: Wilson Malcolm J. , Fuchs Alan , Gordaninejad Faramarz 
Published: August 2002

AbstractMagnetorheological materials have been used in many applications in recent years. To develop new materials, polyurethane and silicone polymer gels were investigated. Rheology is qualitatively controlled for each system by controlling the concentration of reactants and diluents. The resulting polymers have solid, gel, or liquid states, depending on the crosslinking and dilution. The gels were characterized through kinetic analysis. Differential scanning calorimetry (DSC) was used with analysis methods to find the kinetic properties for diluted and undiluted polyurethane systems. Heat of reaction, order of reaction, preexponential constant, and activation energy were obtained from the experimental DSC data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2733–2742, 2002
Synthesis and characterization of poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers
Authors: Luo Weijun , Li Suming , Bei Jianzhong , Wang Shenguo 
Published: August 2002

AbstractPoly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. The reaction was carried out under mild conditions, using dicyclohexylcarbodiimide as the coupling agent and dimethylaminopyridine as the catalyst. The resulting copolymers were characterized by various analytical techniques, such as GPC, viscometry, 1H‐NMR, FTIR, DSC, X‐ray diffractometry, and contact angle measurement. The results indicated that these copolymers presented outstanding properties pertinent to biomedical use, including better miscibility between the two components, low crystallinity, and hydrophilicity. Moreover, the properties of the copolymers can be modulated by adjusting the block length of the two components or the reaction conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1729–1736, 2002; DOI 10.1002/app.10580
Soft segmental effect of methylene bis(p‐cyclohexyl isocyanate) based thermoplastic polyurethane impregnated with lithium perchlorate/propylene carbonate on ionic conductivity
Authors: Wen Ten‐Chin , Chen Hsuan‐Hsu 
Published: August 2002

AbstractThermoplastic polyurethane (TPU) was employed as the polymer matrix for ion conduction as gelled electrolytes with lithium perchlorate (LiClO4) in propylene carbonate (PC) solution. The TPU was prepared by methylene bis(p‐cyclohexyl isocyanate) as the hard segment while employing both poly(ethylene glycol) (PEG) and poly(tetramethylene glycol) (PTMG) as the soft segments. The copolymer comprising both PEG and PTMG was prepared such that it possessed the combined characteristics of good conductivity from the former and good mechanical properties from the latter. All the polymers were characterized by gel permeation chromatography, differential scanning calorimetry, and Fourier transform IR spectroscopy. The conductivity data were obtained from alternating current impedance experiments. The results revealed that the copolymer containing both PEG and PTMG as the soft segments showed better performance than TPU containing either PEG or PTMG. The copolymer TPU(PEG/PTMG) proved to be a good gelled electrolyte from 5 to 85°C. This copolymer, impregnated with 150% LiClO4/PC, possessed good mechanical strength and conductivity as high as 10−3 S/cm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 935–942, 2001
Transesterification reaction kinetics of poly(ethylene terephthalate/poly(ethylene 2,6‐naphthalate) blends
Authors: Shi Yu , Jabarin Saleh A. 
Published: August 2002

AbstractThe transesterification reaction of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends during melt‐mixing was studied as a function of blending temperature, blending time, blend composition, processing equipment, and different grades of poly(ethylene terephthalate) and poly(ethylene 2,6‐naphthalate). Results show that the major factors controlling the reaction are the temperature and time of blending. Efficiency of mixing also plays an important role in transesterification. The reaction kinetics can be modeled using a second‐order direct ester–ester interchange reaction. The rate constant (k) was found to have a minimum value at an intermediate PEN content and the activation energy of the rate constant was calculated to be 140 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2422–2436, 2001
Effects of processing parameters on axial stiffness of self‐reinforced polyethylene composites
Authors: Amer Maher S. , Ganapathiraju Sunil 
Published: August 2002

AbstractSelf‐reinforced polyethylene composites have proven to be promising candidate materials for a number of wear‐resistance and bioimplant applications. In this study, we investigated the effects of processing parameters on the elastic modulus of self‐reinforced high‐density polyethylene (HDPE) composites. The processing parameters investigated were the cooling rate, processing pressure, temperature, and duration. Our results showed an optimum processing temperature, pressure, and duration that were matrix‐dependent. In addition, for an HDPE matrix, the slower the composite cooling rate was, the higher the composite modulus was. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1136–1141, 2001
Kinetic study of olefin polymerization with a supported metallocene catalyst. III. Ethylene homopolymerization in slurry
Authors: Chakravarti S. , Ray W. Harmon 
Published: August 2002

AbstractA kinetic study of ethylene homopolymerization is conducted with a supported unbridged metallocene catalyst in a slurry reactor. The effects of operational parameters such as the reaction temperature and pressure on kinetics are investigated. The kinetic parameters which have been determined for this particular catalyst from previous gas phase studies are used in a slurry reactor model to predict the polymerization behavior under various reaction conditions. The experimental data compare favorably with the predictions from this model. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2901–2917, 2001
Mechanical relaxation processes of wood in the low‐temperature range
Authors: Obataya Eiichi , Norimoto Misato , Tomita Bunichiro 
Published: August 2002

AbstractThe dynamic viscoelastic properties of untreated and chemically modified wood specimens were determined in the temperature range 123 to 293 K and at constant frequencies. Absolutely dry wood specimens exhibited one relaxation process labeled γ at around 180 K, being attributed to the motions of methylol groups in the amorphous region of the wood constituents. The changes in the γ process due to the chemical modifications were explained by the reduction in the original γ loss peak due to the decrease of methylol groups, and an additional relaxation induced by the other groups introduced. With moisture adsorption, an additional relaxation labeled β was induced at 220–240 K. It appeared only when the wood adsorbed moisture irrespective of chemical modifications, and its characteristics were not affected by the formaldehyde and PEG treatments involving the remarkable changes in the mobility of amorphous molecules. These results suggested that the dominant mechanism of β relaxation was not the segmental motions of the main chain, but the motion of the adsorbed water molecules. The positive activation entropy of the β relaxation was interpreted to reflect rearrangement of the adsorption sites required for the rotation of the adsorbed water molecules. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3338–3347, 2001
Photopolymerizable liquid encapsulants for microelectronic devices: Thermal and mechanical properties of systems with reduced in‐mold cure times
Authors: Baikerikar Kiran K. , Scranton Alec B. 
Published: August 2002

AbstractPhotopolymerizable liquid encapsulants (PLEs) for microelectronic devices may offer important advantages over traditional transfer molding compounds, including reduced in‐mold cure times, lower thermal stresses, and reduced wire sweep. In this contribution, we discuss an encapsulation process based upon a low viscosity resin that cures rapidly upon exposure to UV light. These highly filled PLEs are comprised of an epoxy novolac‐based vinyl ester resin (∼25 wt %), fused silica filler (70–74 wt %), photoinitiator, silane coupling agent, and, in some cases, a thermal initiator. We have characterized the material properties (flexural strength and modulus, coefficient of thermal expansion, glass transition temperature, and thermal stress parameter) of PLEs cured with UV illumination times of 60, 90, and 120 s, as well as, the thermal conductivity and adhesive peel strength of PLEs photocured for 90 s. In addition, we investigated the effect of the fused silica loading and the initiation scheme on these properties. The results indicate that the PLEs are very promising for microelectronic encapsulation. These liquid encapsulants cure (to an ejectable hardness) in 1 min for an initiating light intensity of 200 mW/cm2, and exhibit appropriate values for the thermal and mechanical properties listed above. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3449–3461, 2001
Relationship between molecular structure and moisture‐retention ability of carboxymethyl chitin and chitosan
Authors: Chen Lingyun , Du Yumin , Wu Huiqing , Xiao Ling 
Published: August 2002

AbstractCarboxymethyl chitins and chitosans (CM‐chitins, CM‐chitosans) of different substitution sites were prepared under different reaction conditions, and partially depolymerized carboxymethyl chitins of various molecular weights from 24.8 × 104 to 0.26 × 104 were obtained by degrading with chemical reagents. Degree of substitution (DS) was estimated by potentiometric titration. Substitution site was confirmed by infrared and 13C‐NMR spectra. Molecular weights were determined with gel permeation chromatography and gel permeation chromatography combined with laser light scattering (GPC‐LLS). Moisture‐absorption and retention abilities of these compounds were tested in comparison with those of hyaluronic acid (HA). The results reveal that 6‐carboxymethyl group in the molecular structure of chitin and chitosan is a main active site responsible for moisture retention. Although carboxymethylation at OH‐3 and N position is not essential, they contribute to the ability. Moisture‐retention ability is also related to molecular weight; that is, higher molecular weight helps to improve moisture‐retention ability. 6‐O‐CM‐chitin (chitosan) with a DS above 0.8 and molecular weight higher than 24.8 × 104 has the potential to substitute for HA for use in cosmetics and clinical medicine. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1233–1241, 2002