bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dark cure studies of cationic photopolymerizations of epoxides: Characterization of kinetic rate constants at high conversions
Authors: Sipani Vishal , Kirsch Ann , Scranton Alec B. 
Published: July 2004

AbstractThe effective propagation rate constant (kp; averaged over all the propagating active centers) was characterized for solvent‐free cationic photopolymerizations of phenyl glycidyl ether over the entire range of conversions, including the high conversion regime in which mass transfer limitations become important. The profile for the kp as a function of conversion was found to exhibit a constant plateau value at low to intermediate conversions, followed by a monotonic increase above a threshold value of conversion. To explain this trend, it is proposed that at high conversion the diffusional mobility of the photoinitiator counterion is reduced whereas the mobility of the cationic active center remains high because of reactive diffusion. Therefore, with increasing conversion, the average distance between the active centers and counterions may increase, resulting in an increase in the propagation rate constant. The profiles for the kp values were investigated as a function of the temperature, photoinitiator anion, and photoinitiator concentration. As the photoinitiator concentration was increased, the plateau value of the effective propagation rate constant decreased whereas the threshold conversion increased. All of the experimental trends are consistent with the proposed increase in ion separation at high conversions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4409–4416, 2004
Samarium enolate on crosslinked polystyrene beads. III. Anionic initiator for well‐defined synthesis of poly(hydroxyethyl methacrylate) on solid support
Authors: Tanaka Masayoshi , Sudo Atsushi , Endo Takeshi 
Published: July 2004

AbstractA solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004
Synthesis and ring‐opening polymerization of new monoalkyl‐substituted lactides
Authors: Trimaille Thomas , Möller Michael , Gurny Robert 
Published: July 2004

AbstractNew monoalkyl‐substituted lactides were synthesized by reaction of α‐hydroxy acids with 2‐bromopropionyl bromide, and polymerized with various catalysts in the presence of benzyl alcohol by ring‐opening polymerization (ROP). The classic tin(II) 2‐ethylhexanoate (Sn(Oct)2) catalyst was leading to polymers with narrow distribution and predictable molecular weights, in polymerizations in bulk or toluene at 100 °C. The polymerization rate was corresponding to the steric hindrance of the alkyl substituents, such as butyl, hexyl, benzyl, isopropyl, and dimethyl groups. A yield of 83% was obtained with the hexyl‐substituted lactide after 1 h of polymerization. Excellent conversions (97%) could be achieved by using the alternative catalyst 4‐(dimethylamino)pyridine (DMAP). This latter organic catalyst was most efficient in polymerizing the more steric‐hindered lactides with good molecular weight and polydispersity control, in comparison to the tin(II) 2‐ethylhexanoate and tin(II) trifluoromethane sulfonate [Sn(OTf)2] catalysts. The efficiency of the DMAP catalyst and the variability of the monomer synthesis route for new alkyl‐substituted lactides allow to prepare and to envision a wide range of new functionalized polylactides for the elaboration of tailored materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4379–4391, 2004
Synthesis and characterization of polyurethane–urea nanoparticles containing methylenedi‐p‐phenyl diisocyanate and isophorone diisocyanate
Authors: Cheong In Woo , Kong Hyun Chul , An Jeong Ho , Kim Jung Hyun 
Published: July 2004

AbstractWater‐based polyurethane–urea (WPUU) nanoparticles containing 4,4′‐methylenedi‐p‐phenyl diisocyanate (MDI) and isophorone diisocyanate (IPDI) were synthesized by a stepwise prepolymer mixing process, that is, the consecutive formation of hydroxyl‐terminated and isocyanate‐terminated polyurethane prepolymers. The reaction behavior, chemical structure, and consequent morphology of the polyurethane prepolymers and WPUU were investigated with Fourier transform infrared (FTIR), gel permeation chromatography, and NMR techniques with MDI concentrations ranging from 0 (pure IPDI) to 50% with respect to the total moles of isocyanate. Wide‐angle X‐ray diffraction and differential scanning calorimetry patterns showed that the crystallinity of WPUU, which mostly originated from crystallizable poly(tetramethylene adipate) polyol, was significantly affected by the MDI content. Both the crystallinity and melting temperature of WPUU decreased as the MDI content increased. Deconvoluted relative peak areas of the carbonyl region in the FTIR spectrum revealed that the effect of hydrogen bonding among the hard segments became favorable as the MDI content increased, whereas the hydrogen bonding of the soft segments significantly decreased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4353–4369, 2004
Click chemistry in materials synthesis. 1. Adhesive polymers from copper‐catalyzed azide‐alkyne cycloaddition
Authors: Díaz David D. , Punna Sreenivas , Holzer Philipp , McPherson Andrew K. , Sharpless K. Barry , Fokin Valery V. , Finn M. G. 
Published: July 2004

AbstractThe copper(I)‐catalyzed cycloaddition reaction between azides and alkynes has been employed to make metal‐adhesive materials. Copper and brass surfaces supply the necessary catalytic Cu ions, and thus the polymerization process occurs selectively on these metals in the absence of added catalysts. Alternatively, copper compounds can be added to monomer mixtures and then introduced to reducing metal surfaces such as zinc to initiate polymerization. The resulting materials were found to possess comparable or superior adhesive strength to standard commercial glues, and structure‐activity correlations have identified several important properties of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4392–4403, 2004
Thermodynamic interactions in blends of poly(4‐tert‐butyl styrene) and polyisoprene by small‐angle neutron scattering
Authors: Yurekli Koray , Krishnamoorti Ramanan 
Published: July 2004

AbstractThe thermodynamic interactions between poly(4‐tert‐butyl styrene) [P(4tBS)] and 1,4‐polyisoprene (PI; both hydrogenous) were obtained as functions of the temperature, PI molecular weight, and blend composition through the examination of miscible ternary blends of these two components with a common miscible labeled polymer [90% 1,2‐deuterated polybutadiene (dPBD)] with small‐angle neutron scattering. The thermodynamic interaction parameters between P(4tBS) and dPBD and between P(4tBS) and PI increased with increasing temperature and were consistent with lower critical solution temperature behavior. Although the binary blends of P(4tBS) and dPBD exhibited phase separation at elevated temperatures, the thermodynamic interaction parameters between P(4tBS) and PI remained large and negative and independent of the PI molecular weight. Finally, the thermodynamic interactions for PI and P(4tBS) depended strongly on the ratio of PI to P(4tBS) and were also sensitive to the amount of dPBD present in the ternary blend. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3204–3217, 2004
Transformation of phase size distribution into scattering intensity
Authors: Bauer Barry J. 
Published: July 2004

AbstractA practical method of calculating the small‐angle scattering intensity and the density correlation function from the phase size distribution is presented for a sample with a random two‐phase morphology. The correlation function can be calculated in terms of joint probability distribution functions of the phase size distributions of the two individual phases with information from the chord length distribution. The phase size distribution is approximated as a weighted sum of exponentials, which is then transformed analytically into the correlation function and hence the small‐angle scattering for any combination of phase size distributions of the two phases. This represents an extension of the Debye method for materials with more complex phase size distributions. The inverse problem of calculating the phase size distributions from the small‐angle scattering requires a thermodynamic model or simplifying approximation. An example of the reverse transformation is given for a nanoporous polymer thin film. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3070–3080, 2004
Polymer dynamics in hydrogenous systems by neutron reflectivity
Authors: Esker A. R. , Grüll H. , Satija S. K. , Han C. C. 
Published: July 2004

AbstractNeutron reflectivity is a powerful tool for exploring polymer dynamics above the glass‐transition temperature at short diffusion times in layered thin‐film systems. Recent studies of membrane‐mediated interdiffusion in deuterium‐labeled systems have shown that ultrathin membranes can track the position of the interface in binary polymeric diffusion couples and also can discriminate between perdeuterated and hydrogenous polymers of the same molecular weight. This report shows that similar dynamic information can be obtained for binary hydrogenous polystyrene (hPS) diffusion couples separated by an ultrathin (6‐nm) isopentylcellulose cinnamate (IPCC) membrane on Si wafers (air//hPS/IPCC/hPS//Si, where “//” represents an interface between obviously different phases and “/” represents a dynamic interface between polymeric species). In particular, the air//hPS/IPCC/hPS//Si system provides the same information as perdeuterium‐labeled polystyrene (dPS) diffusion couples separated by the same IPCC membrane (air//dPS/IPCC/dPS//Si). This technique has potential applications for the study of confinement effects on thin‐film dynamics and macromolecular transport across membranes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3248–3257, 2004
Effect of random and block copolymer additives on a homopolymer blend studied by small‐angle neutron scattering
Authors: Voge Gretchen , Fosser Kari , Waldow Dean , Briber Robert , Halasa Adel 
Published: July 2004

AbstractSmall‐angle neutron scattering (SANS) has been employed to study a blend of polystyrene and polybutadiene modified by copolymer additives. SANS data from the one‐phase region approaching the phase boundary has been acquired for blends modified by random and diblock copolymers that have equal amounts of styrene and butadiene monomers as well as a random copolymer with an unequal monomer composition. The binary blend is near the critical composition, and the copolymer concentrations are low at 2.5% (w/w). The data have been fitted with the random‐phase approximation model (binary and multicomponent versions) to obtain Flory–Huggins interaction parameters (χ) for the various monomer interactions. These results are considered in the context of previous light scattering data for the same blend systems. The SANS cloud points are in good agreement with previous results from light scattering. The shifts in the phase boundary are due to the effects of the additives on the χ parameter at the spinodal. All the additives appear to lower the χ parameter between the homopolymers; this is in conflict with the predicted Flory–Huggins behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3191–3203, 2004
Dominance hierarchy in a herd of female eland antelope (Taurotragus oryx) in captivity
Authors: Wirtu G. , Pope C.E. , Vaccaro J. , Sarrat E. , Cole A. , Godke R.A. , Dresser B.L. 
Published: July 2004

AbstractThe dominance hierarchy of a group of adult female elands (n=10) kept in captivity was followed for 34 months. Outcomes of dominance relationships at the beginning and end of the study were compared. A clear dominance hierarchy existed in the herd. The dominance pattern was complex, but triads were predominantly (95%) transitive or linear. Reversal of dominance occurred in 12 dyads (27%), of which eight (67%) involved a single female. Two females shared the most dominant rank at the beginning of the study. One of these two females and another female later assumed the highest dominance rank on different occasions. A single female remained most subordinate throughout the study period. The correlation between body weight and dominance rank was not significant (r=0.46; P=0.21). Similarly, dominance rank was not associated with the taming potential of the females. However, the median dominance value increased in females with good taming potential, while it decreased in those with poor taming potential. In conclusion, captive eland antelope have a dynamic and complex dominance hierarchy that is predominantly linear. Zoo Biol 23:323–333, 2004. © 2004 Wiley‐Liss, Inc.
Thermal characteristics of wild and captive Micronesian kingfisher nesting habitats
Authors: Kesler Dylan C. , Haig Susan M. 
Published: July 2004

AbstractTo provide information for managing the captive population of endangered Guam Micronesian kingfishers (Halcyon cinnamomina cinnamomina), four biologically relevant thermal metrics were compared among captive facilities on the United States mainland and habitats used by wild Micronesian kingfishers on the island of Pohnpei (H. c. reichenbachii), Federated States of Micronesia. Additionally, aviaries where kingfishers laid eggs were compared to those in which birds did not attempt to breed. Compared to aviaries, habitats used by wild Pohnpei kingfishers had 3.2°C higher daily maximum and minimum temperatures and the proportion of time when temperatures were in the birds' thermoneutral zone was 45% greater. No differences were found in the magnitude of temperature fluctuation in captive and wild environments. In captive environments in which birds bred, daily maximum temperatures were 2.1°C higher and temperatures were within the thermoneutral zone 25% more often than in the aviaries where the kingfishers did not breed. No differences were found in the magnitude of temperature fluctuation or the daily minimum temperature. Results suggest that the thermal environment has the potential to influence reproduction, and that consideration should be given to increasing temperatures in captive breeding facilities to improve propagation of the endangered Micronesian kingfisher. Zoo Biol 23:301–308, 2004. Published 2004 Wiley‐Liss, Inc.
Calculation of longevity and life expectancy in captive elephants
Authors: Wiese Robert J. , Willis Kevin 
Published: July 2004

AbstractThe concepts of longevity (longest lived) and life expectancy (typical age at death) are common demographic parameters that provide insight into a population. Defined as the longest lived individual, longevity is easily calculated but is not representative, as only one individual will live to this extreme. Longevity records for North American Asian elephants (Elephas maximus) and African elephants (Loxodonta africana) have not yet been set, as the oldest individuals (77 and 53 years, respectively) are still alive. One Asian elephant lived to 86 years in the Taipei Zoo. This is comparable to the maximum (though not typical) longevity estimated in wild populations. Calculation of life expectancy, however, must use statistics that are appropriate for the data available, the distribution of the data, and the species' biology. Using a simple arithmetic mean to describe the non‐normally distributed age at death for elephant populations underestimates life expectancy. Use of life‐table analysis to estimate median survivorship or survival analysis to estimate average survivorship are more appropriate for the species' biology and the data available, and provide more accurate estimates. Using a life‐table, the median life expectancy for female Asian elephants (Lx=0.50) is 35.9 years in North America and 41.9 years in Europe. Survival analysis estimates of average life expectancy for Asian elephants are 47.6 years in Europe and 44.8 years in North America. Survival analysis estimates for African elephants are less robust due to less data. Currently the African elephant average life expectancy estimate in North America is 33.0 years, but this is likely to increase with more data, as it has over the past 10 years. Zoo Biol 23:365–373, 2004. © 2004 Wiley‐Liss, Inc.
A comparison of responses by three broadband radiometers to different ultraviolet‐B sources
Authors: Gehrmann W.H. , Horner J.D. , Ferguson G.W. , Chen T.C. , Holick M.F. 
Published: July 2004

AbstractThree types of broadband ultraviolet‐B (UVB) radiometers were shown to display different irradiances from the same light source. Also, natural light and different lamp types were shown to have different vitamin D–synthesizing potential. Equations relating the irradiance readings from UVB radiometers from Gigahertz‐Optik Inc., UVP Inc., and Spectronics Corp. to in vitro vitamin D–synthesizing potential are reported for four UVB sources. Zoo Biol 23:355–363, 2004. © 2004 Wiley‐Liss, Inc.
Comparison of fecal storage methods for steroid analysis in black rhinoceroses (Diceros bicornis)
Authors: Galama Wieke T. , Graham Laura H. , Savage Anne 
Published: July 2004

AbstractMany field studies and conservation programs for wildlife species include noninvasive endocrine monitoring of gonadal function. Freezing fecal samples immediately after collection until further analysis is often not a viable option for researchers in remote areas. Phase 1 of this study was designed to compare different methods of preserving fecal samples over several time periods (30, 90, or 180 days) in order to determine which method provided the most accurate and reliable technique for measuring fecal progestagens. Fecal samples were collected from two female black rhinoceroses (Diceros bicornis) housed at Disney's Animal Kingdom, Lake Buena Vista, FL. We compared three storage methods: 1) storing fecal samples without processing or preservatives (untreated), 2) storing an aliquot of fecal sample in 80% methanol (MeOH), and 3) drying the fecal sample in a solar box cooker prior to storage. Control samples (day 0) were collected and extracted, and then stored at −20°C until they were analyzed. Phase 2 of the study was designed to examine the effects of long‐term storage (up to 180 days) on fecal progestagen profiles that reflect reproductive activity (pregnancy and estrous cycles). In samples obtained from a pregnant female and stored for 30 days, there were no significant differences in fecal progestagen concentrations between the three treatment conditions. However, the mean concentrations of progestagens (± SE) in untreated samples increased significantly from 8.3 ± 0.3 µg/g wet weight feces at day 0 to 17.7 ± 5.1 µg/g feces at day 90, and 17.8 ± 4.7 µg/g feces at day 180. Samples that were collected from a pregnant female and stored in 80% MeOH or dried in the solar box correlated with controls (r=0.86 and 0.87, respectively; P<0.05) at day 180. In contrast, samples that were stored without preservatives for 180 days did not correlate with controls (r=0.35, P>0.05). Progestagen concentrations from samples of the estrous cycling female showed similar results. In conclusion, fecal samples dried in a solar box cooker or stored in 80% MeOH maintained absolute and relative progestagen concentrations for at least 180 days when they were stored outdoors and exposed to the climatic conditions of central Florida. Both methods can have significant applications for the study of reproductive events in areas where access to electricity is limited. Zoo Biol 23:291–300, 2004. © 2004 Wiley‐Liss, Inc.
Long‐horizon abnormal performance following rights issues and placings: Additional evidence from the U.K. market
Authors: Ho Keng‐Yu 
Published: July 2004

AbstractWe revisit the long‐horizon abnormal performance of U.K. firms following rights issues and placings over the period 1989–1997. We make the following contributions relative to prior research. First, we use, as far as we are aware, a more comprehensive data set of rights issues and placings than hitherto studied for the U.K. market. We thus exploit the fact that issuing new equity predominantly through rights issues is a feature of the U.K. equity market that differs from the U.S. and other markets, where public offers dominate seasoned equity issues. Second, we study both the pre‐ and post‐offer long‐horizon performance, complementing previous research that focuses only on announcement‐day wealth effects. Third, we apply various metrics and revisit the evidence of long‐horizon post‐offer underperformance reported in previous research. We find, however, little evidence of long‐horizon post‐offer underperformance for U.K. firms following issues of equity through rights issues or by placings.
EC_oligos: automated and whole-genome primer design for exons within one or between two genomes
Authors: Liu Shaolin , Tinker Nicholas A. , Molnar Stephen J. , Mather Diane E. 
Published: July 2004

Abstract
Summary: EC_oligos designs oligonucleotides (oligos) from exons of annotated genomic sequence information. It can automatically and rapidly select oligos that are conserved between two sets of sequence data, and can pair up oligos for use as PCR primers. It can do this on a whole-genome scale and according to user-defined criteria.
Availability: The source code, executable program and user manual are available at ftp://ftp.ebi.ac.uk/pub/software/dos/EC_oligos/.
SelSim: a program to simulate population genetic data with natural selection and recombination
Authors: Spencer Chris C. A. , Coop Graham 
Published: July 2004

Abstract
Summary: SelSim is a program for Monte Carlo simulation of DNA polymorphism data for a recombining region within which a single bi-allelic site has experienced natural selection. SelSim allows simulation from either a fully stochastic model of, or deterministic approximations to, natural selection within a coalescent framework. A number of different mutation models are available for simulating surrounding neutral variation. The package enables a detailed exploration of the effects of different models and strengths of selection on patterns of diversity. This provides a tool for the statistical analysis of both empirical data and methods designed to detect natural selection.
Availability: http://www.stats.ox.ac.uk/mathgen/software.html
Supplementary information: http://www.stats.ox.ac.uk/mathgen/software.html
Microarray Data Analysis Toolbox (MDAT): for normalization, adjustment and analysis of gene expression data
Authors: Knowlton Nicholas , Dozmorov Igor M. , Centola Michael 
Published: July 2004

Abstract
Summary: We introduce a novel Matlab toolbox for microarray data analysis. This toolbox uses normalization based upon a normally distributed background and differential gene expression based on five statistical measures. The objects in this toolbox are open source and can be implemented to suit your application.
Availability: MDAT v1.0 is a Matlab toolbox and requires Matlab to run. MDAT is freely available at http://microarray.omrf.org/publications/2004/knowlton/MDAT.zip