bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficiency parameters of nitrogen in hog and cattle manure in the second year following application
Authors: Wen Guang , Schoenau Jeff J. , Charles Julian L. , Inanaga Shinobu
Published: September 2003

The efficiency of nitrogen (N) derived from different manures in the years following application must be determined to optimize use of N and reduce impact on the environment. Five N efficiency parameters that were originally developed for commercial inorganic N fertilizers were selected to measure the manure N efficiency in the second year following application of liquid hog and solid cattle manure in semiarid east‐central Saskatchewan, Canada. The manures were applied at two sites (Dixon and Burr) at four rates covering a range from zero to 912 kg N ha–1in 1997. A canola (Brassica napusL.) crop was grown in 1997 followed by a spring wheat (Triticum aestivumL.) in 1998 without fertilization. Tested by the wheat, N utilization efficiency (NUE) was similar between the two manures at either site, but it was higher at Dixon site, where the soil properties were better, than at the Burr site (P < 0.07) with cattle manure. Nitrogen physiological efficiency (NPE) was not affected by either manure source or soil. At the Burr site, N agronomic efficiency (NAE) and N recovery rate (NRR) were all higher with the hog than with the cattle manure (P< 0.08 andP< 0.07, respectively), but N harvest index (NHI) was lower with the hog than with the cattle manure (P< 0.04). The similar trends of the NAE, NRR, and NHI between the hog and cattle manure were also found at the Dixon site. However, the differences in NRR between the hog and cattle manure in the second year was rather small in contrast to the large differences in the year of application. Despite that the wheat crop utilized residual hog and cattle manure N equally efficient in producing grain yield, a higher grain N concentration and a higher NHI with the cattle than with the hog manure revealed different N supply dynamics between the two. Possibly due to the low proportion of ammonium (NH3)‐N in the total N and the high C : N ratio in the cattle manure, mineralization of cattle manure N provided more available N in the later stage of wheat growth than did the hog manure. The N efficiency parameters were useful tools in understanding the impact of residual manure N on wheat production on the Canadian prairies.
Evaluation of soil P‐test values of canton Geneva/Switzerland in relation to P loss risks
Authors: Celardin Fredi
Published: September 2003

The P status of the soils of Geneva is routinely determined by two independent chemical extractions. The P amounts extracted independently by an aqueous solution of ammonium acetate 0.5 M + EDTA 0.02 M (pH 4.65) (1:10 solid weight : solution volume, 60 minutes) and by H2O (1 : 10 solid weight : solution volume, 60 minutes) were assumed to represent mobilizable and mobile phosphorus pools. The best correlations with the data from 1023 crop field soil samples in Geneva canton during the years 1994 to 2000 were obtained by power functions if the data were grouped in two distinct pH ranges:

pH 4.6–6.5: (P‐AAE) = 16.436 (P‐H2O) 0.6083; R2 = 0.625; n = 166,

pH 6.6–8.6: (P‐AAE) = 25.582 (P‐H2O) 0.6518; R2 = 0.47; n = 857.

The derivatives of these functions are representative of apparent P‐buffering power. Environmentally sound threshold values for P‐H2O and P‐AAE are estimated by calculating the change points first of these P‐AAE (quantity) against P‐H2O (intensity) curves and second P‐buffering power against P‐H2O or P‐AAE curves.

The change points obtained from the smoothed quantity‐intensity data were:

pH 4.6–6.5: P‐H2O = 3.8 mg kg–1 and P‐AAE = 16.436 (3.8)0.6083 = 37.0 mg kg–1; n = 166,

pH 6.6–8.6: P‐H2O = 2.5 mg kg–1 and P‐AAE = 25.582 (2.5)0.6518 = 46.5 mg kg–1; n = 857.

The change‐points for P‐buffering power curves occurred at

pH 4.6–6.5: P‐H2O = 1.3 mg kg–1; P‐AAE = 19.7 mg kg–1; n = 166,

pH 6.6–8.6: P‐H2O = 1.3 mg kg–1; P‐AAE = 20.6 mg kg–1; n = 857.

The threshold buffering powers were:

pH 4.6–6.5: d(P‐AAE)/d(P‐H2O) = 9.998 (P‐H2O) –0.3917 = 9.0,

pH 6.6–8.6: d(P‐AAE)/d(P‐H2O) = 16.674 (P‐H2O) –0.3482 = 15.2.

These results show that presently only about 25 % of the crop soils of Geneva canton were within these safe limits. The possibility of applying values of this magnitude which are significantly lower than officially recommended reference levels for phosphorus fertilizer recommendations is supported by recent agronomic investigations.
Do different methods used to estimate soil phosphorus availability across Europe give comparable results?
Authors: Neyroud Jean‐A. , Lischer Peter
Published: September 2003

Each European country is using its own method for the determination of phosphorus availability to plants, together with an appropriate interpretation scheme of the P status and fertilizer recommendations. In order to compare systems, a soil exchange program was organized: 16 P methods were compared on 135 soils from 12 countries. The amount of extracted P decreased in the order Ptotal > Poxal. > PAL > PMe3 > PBray > PAAEDTA, PDL, PCAL > POlsen > Ppaper strip, PAAAc, PMorgan > PH2O, PCO2, PCaCl2. Isotopically exchangeable P was also measured. A large variability was observed in the results obtained by laboratories using the same method, thus demonstrating the great importance of an identical lab procedure as a prerequisite to any comparison. The traditional correlation/regression approach revealed its limitations when applied to non‐homogeneously distributed data and was replaced by more robust techniques that showed laboratory differential bias and confidence intervals of the log‐transformed values. Even though all the methods reacted in the same way to increasing amounts of added P in several trials, there were wide differences between results obtained with different methods. The interpretation schemes for P status were also compared and revealed that about 50 % of the tested soils were P‐deficient. This observation appears not to be in line with a generally high P fertilization during the last decades in Europe and should lead to a better evaluation of the plant‐available soil phosphorus.
Approaches to calculating P balance at the field‐scale in Europe
Authors: Tunney Hubert , Csath Peter , Ehlert Phillip
Published: September 2003

Policies for mitigating phosphorus (P) loss from agriculture are being developed in a number of European countries and calculation of P balance at farm‐gate or field‐scale is likely to be a part of such policies. The aim of the paper was to study P balance at the field‐scale in 18 countries that participated in the European Union's (EU) European Co‐operation in the Field of Scientific and Technical Research (COST) action on “Quantifying the Agricultural Contribution to Eutrophication (COST 832)”. A questionnaire related to P balance at the field‐scale was sent to representatives in the 18 countries and all replied. The field as a unit is defined differently in the various European agricultural systems. The identification of the inputs and outputs differ among the countries. For example, P losses may or may not be taken into account in balances. Phosphorus balance at the field‐scale is used in all countries in the context of soil analysis and P recommendations for crops and advisory and research purposes, while only a few countries use it for policy purposes (agri‐environmental). There is wide variation in P balances between countries in relation to soil fertility and vulnerability of water to eutrophication from nutrients from agricultural sources. In several eastern European countries, Hungary for example, fertilizer P use has dropped to about one tenth of the levels used in the 1980's. Many of these countries now have a negative P balance. In western European countries, by contrast, although fertilizer P use has decreased in recent years, the average input is higher than the average off take, and soil test phosphorus (STP) values remains high and continue to increase in some areas. Twelve different soil extractants for STP are used in Europe, and their interpretation can hinder direct comparisons. Calculating P balance at the field‐scale involves approximations in estimating inputs and outputs and spatial variations in fertility in individual fields. Accuracy of data and standardization of methods for calculating balances with inputs and outputs will be a challenge for the future development of a sustainable agriculture in Europe.
The conceptual basis for a decision support framework to assess the risk of phosphorus loss at the field scale across Europe
Authors: Heathwaite Louise , Sharpley Andrew , Bechmann Marianne
Published: September 2003

We report a conceptual framework for a simple screening tool to evaluate the vulnerability of different fields in the landscape to phosphorus (P) loss within the European agricultural context. Our work builds on the principles established for the P Index system developed in the United States. We examine the differing needs and criteria for a range of EU member states and EFTA countries and highlight essential and optional criteria for inclusion in the decision support framework depending on their ecoregional characteristics. A framework such as this, meets in principle, the needs of the COST832 Action ‘Quantifying the Agricultural Contribution to Eutrophication’ as it deals with diffuse nutrient sources from agriculture, and aids more targeted use of practical strategies to mitigate nutrient losses to minimise the potential for the eutrophication of receiving waters.
Phosphorus dynamics and export in streams draining micro‐catchments: Development of empirical models
Authors: Kronvang Brian , Bechmann Marianne , Pedersen Morten L. , Flynn Nicola
Published: September 2003

Annual total phosphorus (TP) export data from 108 European micro‐catchments were analyzed against descriptive catchment data on climate (runoff), soil types, catchment size, and land use. The best possible empirical model developed included runoff, proportion of agricultural land and catchment size as explanatory variables but with a low explanation of the variance in the dataset (R2 = 0.37). Improved country specific empirical models could be developed in some cases. The best example was from Norway where an analysis of TP‐export data from 12 predominantly agricultural micro‐catchments revealed a relationship explaining 96 % of the variance in TP‐export. The explanatory variables were in this case soil‐P status (P‐AL), proportion of organic soil, and the export of suspended sediment. Another example is from Denmark where an empirical model was established for the basic annual average TP‐export from 24 catchments with percentage sandy soils, percentage organic soils, runoff, and application of phosphorus in fertilizer and animal manure as explanatory variables (R2 = 0.97).
Incidental phosphorus losses – are they significant and can they be predicted?
Authors: Withers Paul J. A. , Ulén Barbro , Stamm Christian , Bechmann Marianne
Published: September 2003

Fresh applications of phosphorus (P) may cause ‘incidental’ losses of dissolved and particulate P forms in land runoff when rainfall interacts directly with fertilizers and manures which are spread, or excreted, onto the soil surface. Research indicates that when incidental P losses (IPL) occur, they often make the dominant (50–98 %) contribution to measured P loads in surface and sub‐surface runoff from field plots, with increased risk of eutrophication where P‐enriched runoff is routed directly to the watercourse. Rates of P loss are temporally and spatially very variable (< 1 to 25 % of total P applied) depending on the amount of P applied; the P release properties of the materials applied (% P extractable in water), the timing of storm events after application and the amounts of runoff generated. Large P applications left on the surface of wet, frozen, compacted, and intensively underdrained soils in high rainfall areas are particularly vulnerable to IPL. Concentrations of P in runoff are often greatest during the first storm event following P application, but can remain high for several weeks, or even months after application. Catchment scale impacts are more difficult to quantify due to the effects of dilution with runoff from fields without IPL, and the contributions of P from other sources. Approaches to predicting IPL are discussed and need to be improved in order to assess the contribution of IPL to catchment P loads in river basin management planning. Strategies to control IPL should focus on adoption of more sensitive management practices in fields with a high risk of rapid runoff or preferential flow, and are likely to very effective.
Potential role of phosphate buffering capacity of soils in fertilizer management strategies fitted to environmental goals
Authors: Ehlert Phillip , Morel Christian , Fotyma Mariusz , Destain Jean‐Pierre
Published: September 2003

Sorption behavior and buffering of phosphorus (P) are important, both from an agricultural and an environmental point of view. The objectives of this study were to investigate: (1) the kinetics of the transfer of P from soil to soil solution and assessing P buffering capacity of soils (PBC), as a function of soil solution P; (2) the effect of PBC on soil P status fitted to environmental targets for water quality; (3) the effect of PBC on crop response. PBC was derived from the non‐linear Q‐I curve describing the time‐dependent relationship between plant‐available reserve of soil P (Q) versus soil solution P (I). The Q‐I curve was determined in soil suspension using sorption and isotopic dilution methods for soil samples from French, Swedish, and Dutch field trials. Soils with low PBC values were more sensitive to the loss of P to the environment, required higher critical value in soil solution P to comply with P demand of maize, and had higher change in soil solution P per unit of P budget. In different soils, both the critical soil solution P for maize and the change in soil solution P per unit of P balance varied inversely with PBC. It is concluded that (1) PBC plays a key role in determining the agronomic and environmental threshold levels of available P content in the soils, and (2) PBC is a prerequisite for the development of more environmentally oriented fertilization recommendation systems.
Risk assessment methodologies for predicting phosphorus losses
Authors: Schoumans Oscar F. , Chardon Wim J.
Published: September 2003

Risk assessment parameters are needed to assess the contribution of phosphorus (P) losses from soil to surface water, and the effectiveness of nutrient and land management strategies for the reduction of P loss. These parameters need to take into account the large temporal and spatial variation in P transfer from individual fields arising from (a) changing but predictable factors such as land use, soil P status, P application rates, forms and ways of fertilization and spreading, (b) predictable but inherent factors such as soil type, soil dispersivity, slope and hydrological routing, and (c) unpredictable weather factors such as rainfall amount and intensity. In most situations, water transport is the driving force of P loss from agricultural land to surface water. Therefore, the hydrological pathways determine to a large extent the relevance of these different factors. Over the last decade several soil P tests have been proposed as a first step to link field conditions to risk of P loss. The major reason is that these soil P tests are also meaningful in discussions with farmers. Recently, more complex P loss risk parameters have been derived based on different approaches. However, the scope and purposes of these P loss risk parameters vary remarkably. Finally, there is a need to evaluate the usefulness of new P tests that can be used as an indicator of P loss risk, e.g. in relation to monitoring purposes. The implementation of the EU Water Framework Directive will increase this need.

In this paper, the practicable applicability of P parameters for risk assessment is discussed in relation to purpose, scale (from field, farm to catchment), effectiveness, sensibility etc. Furthermore, a conceptual framework for P indicators is presented and evaluated, based on the outcome of the presentations and the discussions in Zurich.
A bugle call right in the ear
Authors: Hesselbein Frances
Published: September 2003

How do we deliver the message that in a democracy, no one has permission to stand aside?
When ideas lead, people follow
Authors: Flaum Sander A.
Published: September 2003

Effective leaders pursue a great idea, get out of the way, and let the idea lead.
The hidden work of leadership
Authors: Frost Peter J.
Published: September 2003

Sometimes leaders need to clean up after themselves.
Leading technical people
Authors: Glen Paul
Published: September 2003

Yes, geeks march to a different drummer, but they can be led.
Five pillars for leading the client‐focused organization
Authors: Neubauer Joseph
Published: September 2003

Candid observations on leading for growth from ARAMARK's chairman.
Creating a platform for leadership
Authors: Gilmartin Raymond V.
Published: September 2003

Merck's chairman and CEO talks with Leon Martel about the underpinnings of leadership.
A master course in leadership
Authors: Badowski Rosanne
Published: September 2003

A close‐up look at what made Jack Welch such a successful leader.
Enterprise leadership
Authors: Davidson Bill
Published: September 2003

Why pushing power and authority down in the organization isn't all it's cracked up to be.
Making it up and making it happen
Authors: Allen David
Published: September 2003

Making (the right) things happen.
Ethylene Polymerization with Silica‐Supported Nickel‐Diimine Catalyst: Effect of Support and Polymerization Conditions on Catalyst Activity and Polymer Properties
Authors: AlObaidi Fahad , Ye Zhibin , Zhu Shiping
Published: September 2003

Ethylene was polymerized using both homogeneous and modified methylaluminoxane (MMAO)‐treated silica supported nickel‐diimine catalysts (1,4‐bis(2,6‐diisopropylphenyl) acenaphthene diimine nickel(II) dibromide) in a slurry semibatch reactor. The effects of catalyst support and polymerization conditions (ethylene pressure and reaction temperature) on catalyst activity and polymer properties were systematically investigated. The supported catalyst gave far lower activity than the homogeneous catalyst. The activities of both catalyst systems increased with polymerization temperature with a maximum at 40 °C. Compared with the homogeneous catalyst, the supported catalyst system produced polyethylene with a different microstructure. Due to steric effects, the supported catalyst system exhibited lower chain walking rates than the homogeneous catalyst, producing polymers with less branching content and, thus higher melting points. Depending on polymerization conditions, two active site populations were observed during polymerization using supported catalyst; one population remained fixed on the surface of the support, and the other was extracted from the support, exhibiting the same polymerization behavior as the homogeneous catalyst.

DSC thermograms for polyethylene produced with homogeneous and supported catalysts at an ethylene pressure of 50 psig (3.45 · 105 Pa) and reaction temperature 40 °C.

magnified image

DSC thermograms for polyethylene produced with homogeneous and supported catalysts at an ethylene pressure of 50 psig (3.45 · 105 Pa) and reaction temperature 40 °C.
Synthesis and Optical Properties of a Copolymer of Tetrafluoro‐ and Dialkoxy‐Substituted Poly(p‐phenylenevinylene) with a High Percentage of Fluorinated Units
Authors: Babudri Francesco , Cardone Antonio , Farinola Gianluca M. , Naso Francesco , Cassano Tiziana , Chiavarone Luca , Tommasi Raffaele
Published: September 2003

A copolymer of 2,3,5,6‐tetrafluoro‐1,4‐phenylenevinylene and 2,5‐dioctyloxy‐1,4‐phenylenevinylene [co(TFPV‐DOPV)], containing more than 60% of tetrafluorophenylenevinylene monomeric units, was synthesized by the Stille cross‐coupling reaction. Its linear and nonlinear optical properties were investigated. Linear absorption and photoluminescence measurements performed on thin films and solution indicate interchain migration upon excitation. The Z‐scan technique was used to evaluate the third‐order nonlinear susceptibility at λ = 1064 nm. A very high refractive nonlinearity (n2 = (−10 ± 2) × 10−12 cm2 · W−1) was measured with a value one order of magnitude larger than that of the corresponding dialkoxy‐substituted homopolymer.

magnified image
Synthesis of Hyperbranched Poly(phenylene oxide) by Ullmann Polycondensation and Subsequent Utilization as Unimolecular Micelle
Authors: In Insik , Lee Hyosan , Kim Sang Youl
Published: September 2003

A new hyperbranched poly(phenylene oxide) was synthesized from a simple AB2 type monomer, 3,5‐dibromophenol, by Ullmann polycondensation. The bromo‐terminated hyperbranched poly(phenylene oxide) was amorphous (Tg = 120 °C), but showed high thermal stability (T5d = 480 °C in nitrogen). The polymer with the degree of branching of 0.61 showed good solubility in organic solvents. The highly branched nature of the polymer effectively disrupted the crystalline characteristics of the linear poly(phenylene oxide) (Tm = 285 °C). When the bromine end groups of the polymer were transformed to lithium carboxylate groups, the resulting polymer became soluble in water. This carboxylate‐terminated hyperbranched poly(phenylene oxide) showed the characteristics of an unimolecular micelle in aqueous solution and behaved as a host for nonpolar organic guest molecules such as 1,4‐diaminoanthraquinone even under the critical micelle concentration of conventional surfactants.

DSC and TGA curves of the hyperbranched poly(phenylene oxide) 2.

magnified image

DSC and TGA curves of the hyperbranched poly(phenylene oxide) 2.
Microstructure of Metallocene‐Catalyzed Propene/1‐Pentene Copolymers
Authors: Sacchi Maria Carmela , Forlini Fabrizio , Losio Simona , Tritto Incoronata , Wahner Udo M. , Tincul Ioan , Joubert Dawie J. , Sadiku Emmanuel R.
Published: September 2003

The microstructure of propene/1‐pentene copolymers prepared with the metallocene catalysts rac‐Et(Ind)2ZrCl2 and rac‐Me2Si(2‐MeBenz‐[e]Ind)2ZrCl2 was studied by 13C NMR spectroscopy. Both catalysts lead to the formation of random copolymers although rac‐Me2Si(2‐MeBenz‐[e]Ind)2ZrCl2 favors a somewhat higher incorporation of 1‐pentene than rac‐Et(Ind)2ZrCl2. Surprisingly, the presence of 1‐pentene has a significant influence on the stereoregularity of the copolymers formed with rac‐Me2Si(2‐MeBenz‐[e]Ind)2ZrCl2. Propene/1‐pentene copolymers produced with rac‐Et(Ind)2ZrCl2 retained the isotacticity of polypropene and featured only the stereoerror pentads mmmr, mmrr and mrrm typical for enantiomorphic site control. However, propene/1‐pentene copolymers obtained with rac‐Me2Si(2‐MeBenz‐[e]Ind)2ZrCl2 are characterized by a gradual loss of tacticity which is concurrent with an increase in the amount of all irregular pentads. It is proposed that the presence of 1‐pentene can lead to a reversible loss of stereocontrol over a whole sequence of inserted monomer units. Subsequently, more or less atactic blocks are formed besides isotactic blocks.

Percentage of 1‐pentene in the copolymer as function of the feed composition for 1‐pentene/propene copolymers prepared with EI and MBI.

magnified image

Percentage of 1‐pentene in the copolymer as function of the feed composition for 1‐pentene/propene copolymers prepared with EI and MBI.
Relationship between Architecture and Adhesive Properties of Macromolecular Materials, 1
Authors: Baron Amélie , Cloutet Eric , Cramail Henri , Papon Eric
Published: September 2003

This study deals with the preparation of polyurethane‐graft‐poly(n‐butyl acrylate)s copolymers by polymerization of diphenyl‐methane‐4,4‐di‐isocyanate (MDI) with α,α′‐di‐hydroxyl‐poly(n‐butyl acrylate)s of different sizes as macromonomers. The polyaddition has been studied on the basis of kinetic measurements, and the comb‐like structure of the resulting polymer has been well‐established. Such grafted copolymers display specific adhesive properties in connection with their comb‐like architecture.

magnified image
Polyamides X.34: A New Class of Polyamides with Long Alkane Segments
Authors: Ehrenstein Moritz , Smith Paul , Weder Christoph
Published: September 2003

A new series of semi‐crystalline polyamides (PA), which comprise extended aliphatic segments between the amide moieties and which display an interesting amphiphilic character has been synthesized and characterized. The polymers PA‐2.34, PA‐4.34, PA‐8.34, PA‐10.34, and PA‐12.34 were prepared by melt‐polycondensation of salts of tetratriacontanedioic acid and the respective short‐chain diamine. The thermal properties of these polymers were investigated by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. The new polyamides exhibit melting temperatures that depend on the length of the diamine and range between 166 (PA‐12.34) and 190 °C (PA‐2.34). Solid transitions were observed between 38 and 57 °C. The materials displayed a rather limited solubility in common polyamide solvents, but readily dissolved in alkylsulfonic acids. All members of the series formed thermo‐reversible gels in the highly polar sulfuric acid and 1,2,3,4‐tetrahydronaphthalene, reflecting their interesting amphiphilic character. Young's moduli and tensile strengths of melt‐processed, isotropic films of the polyamides investigated were in the range of 0.5–0.7 GPa and 20.30 MPa, respectively, independent of the length of the diamine used.

Melting temperatures of polyamides PA‐X.34 (x) and 1,2,3,4‐tetrahydronaphthalene/PA‐X.34 gels (37.5 wt.‐% polyamide, determined from the second DSC heating scans) (+).

magnified image

Melting temperatures of polyamides PA‐X.34 (x) and 1,2,3,4‐tetrahydronaphthalene/PA‐X.34 gels (37.5 wt.‐% polyamide, determined from the second DSC heating scans) (+).
Hydrolytic Polycondensation of Bisphenol‐A‐Bischloroformate Catalyzed by Phase‐Transfer Catalysts
Authors: Kricheldorf Hans R. , Böhme Sigrid , Schwarz Gert , Schultz Claus‐Ludolf
Published: September 2003

The hydrolytic interfacial polycondensation of bisphenol‐A‐bischloroformate was performed with four different phase‐transfer (PT) catalysts: N‐butylpyridinium bromide, triethylbenzylammonium (TEBA) chloride, tetrabutylammonium hydrogen sulfate, and tetraphenylphosphonium bromide. These polycondensations were conducted at 5 or 35 °C initial reaction temperature. The resulting polycarbonates were characterized by viscosity and SEC measurements and by MALDI‐TOF mass spectrometry. The four PT catalysts gave quite different results with respect to molecular weight and formation of cyclic polycarbonates. The highest molecular weights (number average, $\overline M _{\rm n} \approx 215\;{\rm kDa}$ and weight average, $\overline M _{\rm w} \approx 600\;{\rm kDa}$) were obtained with TEBA‐Cl. Lower temperatures and high feed ratios of TEBA‐Cl proved to be favorable for both high molecular weights and high fractions of cycles. Cyclic polycarbonates were detectable in the mass spectra up to 14 kDa (technical limit of the measurements). Low molecular weights in combination with unreacted chloroformate groups proved that the other PT‐catalysts were less efficient under the given reaction conditions.

MALDI‐TOF mass spectrum of the polycarbonate No. 3b.

magnified image

MALDI‐TOF mass spectrum of the polycarbonate No. 3b.
New Organo‐Soluble Conjugated Polyquinolines
Authors: Krüger Hartmut , Janietz Silvia , Sainova Dessislava , Wedel Armin
Published: September 2003

Polyquinolines are under discussion as n‐type materials for organic field effect transistors, organic light‐emitting diodes and organic solar cells together with other N‐heterocycle‐containing conjugated polymers. But most of these conjugated polyquinolines are not soluble in common organic solvents. Therefore, a new synthetic pathway is presented in this work leading to organo‐soluble polyquinolines. The results of the synthesis and characterization of the obtained new organo‐soluble polyquinolines are shown. The electrochemical reduction and oxidation behavior of these polymers is studied by cyclovoltammetric measurements. All studied polymers can be reversibly oxidized and reduced. The absorption and luminescence properties are investigated. Organic light‐emitting diodes (OLEDs) are prepared from the new polyquinolines as an active single layer. The electroluminescence behavior and the characteristics of the OLEDs are discussed.

Electroluminescence spectra of the LEDs with polymers 8a–c as emissive layers.

magnified image

Electroluminescence spectra of the LEDs with polymers 8a–c as emissive layers.
New Aromatic tert‐Amines for Application as Photoinitiator Components in Photocurable Dental Materials
Authors: Ahn Kwang‐Duk , Han Dong Keun , Lee Suck‐Hyun , Lee Chan‐Woo
Published: September 2003

A new type of aromatic tert‐amine with a bisphenol A (BPA) skeleton has been prepared and applied as a photoinitiator (PI) component for enhancing photosensitivity in formulations of visible light curable dental polymers. Two N,N‐dimethylamino (DMA) groups were incorporated into BPA diglycidyl ether to make 2,2‐bis[4‐(2‐hydroxy‐3‐(p‐N,N‐dimethylaminobenzoyloxy)propyloxy)phenyl]propane (DMABPA). One or two (meth)acryloyl groups were reacted with the hydroxyl groups of DMABPA to obtain the polymerizable, BPA‐based tert‐amines DMABPA‐1M (one methacrylate), DMABPA‐2M (two methacrylates), and DMABPA‐1A (one acrylate). The aromatic tert‐amines and ethyl p‐(N,N‐dimethylamino)benzoate (EDMAB) were combined with a camphorquinone sensitizer to form a photoinitiating system, which was applied in photopolymerizations of dental resin formulations, based on Bis‐GMA as a matrix prepolymer, by visible light exposure. The photoconversion of the formulations using the new aromatic tert‐amines as PIs was determined by the spectral changes in FTIR absorption intensities of methacrylate groups in cast films. High conversion (over 70%) resulted from photopolymerizations with (meth)acrylated DMABPA‐(1M, 2M, and 1A).

magnified image
Novel Glass Fiber‐Reinforced Composites Having a UV and Peroxy Curable Fluoropolymer Matrix
Authors: Turri Stefano , Sanguineti Aldo , Lecchi Romina
Published: September 2003

Novel glass fiber‐reinforced composites were prepared from E‐glass fibers and perfluoropolyether (PFPE), polyurethane acrylate, and methacrylate resins. The PFPE resins were synthesized by a two‐step process and formulated with reactive acrylic diluents obtaining two compositions with different viscosity and fluorine content. These formulations were photocrosslinked by UV‐A radiation and characterized by tensile and dynamic‐mechanical properties as well as by impact resistance. The two UV cured fluoropolymer compositions are high modulus (> 1 GPa), polyphasic materials characterized by a fracture toughness higher than conventional polymer matrices, like epoxies and unsaturated polyesters. Unidirectional laminate composites were also prepared by hand lay‐up and crosslinked both photochemically and thermally. Mechanical characterization of glass fiber‐reinforced composites was carried out by tensile tests and shear adhesion measurements, showing a good fluoropolymer‐glass adhesion strength (ca. 9 MPa). Surface characterization of composites by static contact angle measurements allowed the calculation of the total surface tension γs according to Wu's harmonic mean approximation. Surface tension is very low (< 20 mN/m) suggesting a preferential stratification of PFPE segments at the material‐air interface.

magnified image
Study of the Effects of Gamma Irradiation on the Structure and Physical Properties of Low Density Polyethylene Films Containing Hindered Amine Stabilizers
Authors: Kaci Mustapha , Remili Chérifa , Khima Rochedine , Sadoun Tahar
Published: September 2003

The effect of gamma‐irradiation on the structure, rheology, and mechanical properties of low density polyethylene (LDPE) films containing some new hindered amine stabilizers (HAS) has been investigated and the results obtained were compared to additive free samples. The HAS used involved various structures such as an alkoxyamine, a polymer bound HAS and a HAS modified with siloxane; these are commercially known as Tinuvin 123, Sanduvor PR 31 and Uvasil 299, respectively. It was found that the carbonyl index values measured by FTIR spectroscopy increased linearly with the radiation dose for all the samples studied, however this increase was less pronounced for the stabilized samples. The formation rates of carbonyls followed the order LDPE > LDPE/Uvasil 299 > LDPE/PR 31 > LDPE/Tinuvin 123. The second order derivative UV analysis showed the formation of vinyl groups in the irradiated samples at higher doses (812 kGy), while vinylidene groups were detected only in the films stabilized with PR 31 and Tinuvin 123. The curves of the melt flow rate (MFR) exhibited a fast increase for the unstabilized sample after 67 kGy, indicating the occurrence of chain scission. The stabilized samples on the other hand showed an evident increase in MFR from almost 300 kGy. The contribution of different HAS for the durability of LDPE films under γ rays was evaluated by determining the half‐value‐dose, which is related to the radiation resistance of the material. The results indicated that the presence of HAS in LDPE films improves the half‐value‐dose of those stabilized with Tinuvin 123 by 2.5 times against 2.4 and 2 for PR 31 and Uvasil 299, respectively. These data correlate well with the results obtained by FTIR and MFR measurements. Finally, the higher efficiency of Tinuvin 123 could be assigned to its appropriate oxidation state to enter the stabilization mechanism directly.

An example of the new HAS.

magnified image

An example of the new HAS.
Preparation of Nanoporous Polyimide Films from Poly(urethane‐imide) by Thermal Treatment
Authors: Krishnan P. Santhana Gopala , Cheng Chia Zheng , Cheng Yeo Swee , Cheng Jimmy Wu Chi
Published: September 2003

Nanoporous polyimide films were prepared in two steps. The first step is the preparation of poly(urethane‐imide) films by casting blend solutions containing various weight percentages of poly(amic acid) and phenol blocked polyurethane prepolymer (from 1,6‐hexamethylene diisocyanate and poly(ethylene glycol)). Three poly(amic acid)s were obtained from biphenyltetracarboxylic dianhydride (or) 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride with 1,4‐phenylenediamine (or) 2,5‐dimethyl‐1,4‐phenylenediamine. Poly(urethane‐imide) films were characterized by density and surface energy measurements, AFM, DSC, TMA, mechanical properties and TGA. In the second step, these films were thermally treated above 300 °C to give nanoporous polyimide films. During thermal treatment, less thermally stable urethane domains decomposed, leaving porous polyimide films. The presence of pores was confirmed by scanning electron microscopy (SEM). The dielectric constant of the polyimide film was found to decrease with increasing amounts of urethane content.

A nanoporous polyimide film.

magnified image

A nanoporous polyimide film.
Tensile Fracture and Failure Behavior of Thermoplastic Starch with Unidirectional and Cross‐Ply Flax Fiber Reinforcements
Authors: Romhány Gábor , Karger‐Kocsis József , Czigány Tibor
Published: September 2003

Thermoplastic starch (MaterBi®) based composites containing flax fibers in unidirectional and crossed‐ply arrangements were produced by hot pressing using the film stacking method. The flax content was varied in three steps, viz. 20, 40 and 60 wt.‐%. Static tensile mechanical properties (stiffness and strength) of the composites were determined on dumbbell specimens. During their loading the acoustic emission (AE) was recorded. Burst type AE signal characteristics (amplitude, width) were traced to the failure mechanisms and supported by fractographic inspection. The mechanical response and failure mode of the composites strongly depended on the flax content and the flax fiber lay‐up. It was established that the tensile strength increases until 40 wt.‐% flax fiber content but stays almost constant above this value. In the case of 40 wt.‐% unidirectional fiber reinforcement, the tensile strength of the composite was 3 times greater than that of the pure starch matrix. The flax fiber reinforcement increased the tensile modulus of the pure starch by several orders of amplitude.

SEM picture of the fracture surface of a composite with UD flax reinforcement.

magnified image

SEM picture of the fracture surface of a composite with UD flax reinforcement.
Research on Preparation, Structure and Properties of TiO2/Polythiourethane Hybrid Optical Films with High Refractive Index
Authors: Lü Changli , Cui Zhanchen , Guan Cheng , Guan Jingqi , Yang Bai , Shen Jiacong
Published: September 2003

Hybrid optical films of TiO2‐triethoxysilane‐capped polythiourethane (TCPTU) with high refractive indices have been prepared via an in situ sol‐gel method. The high refractive index triethoxysilane‐capped polythiourethane (TCPTU) was synthesized by polyaddition of the triethoxysilane‐modified trimercaptothioethylamine (TMTEA) and 2,2′‐dimercaptoethylsulfide (MES) with 2,4‐tolylene diisocyanate (TDI). The titania content in the hybrid films can be adjusted from 0 to 80 wt.‐% by the feed ratio of titania precursor [Ti(OBu)4] to polymer (TCPTU). Both FTIR and DSC analyses indicate that there is chemical bonding between the titania domain and the polymer chain. TGA results suggest that the titania of high content was successfully incorporated into polymer matrices and this series of hybrid films have good thermal properties. AFM measurements indicate that in the hybrid films the titania domains are of nanosize scale and the domain size averagely decreases from 60–80 nm to 5–20 nm with increasing content of titania, and the variation of surface roughness for the hybrid films has the same trend. These may be relative to the content of TCPTU and the interaction between titania and polymer (TCPTU). The refractive indices of the hybrid films at 632.8 nm increased from 1 632 to 1 879 as the titania content varied from 0 to 80 wt.‐%.

AFM image of the hybrid film.

magnified image

AFM image of the hybrid film.
Synthesis of Reactive Polymeric Dyes as Textile Auxiliaries
Authors: Altomare Angelina , Ciardelli Francesco , Faralli Giada , Solaro Roberto
Published: September 2003

New polymeric materials containing amino‐substituted azobenzene chromophores and reactive functional groups and characterized by some hydrophilicity were prepared with the aim of investigating alternative textile dyeing routes. The indicated materials were obtained either by copolymerization of suitable monomers or by modification of preformed polymers. In both cases commercial 4‐amino‐2′,3‐dimethylazobenzene (FG) was used as chromogenic compound. According to the first synthetic strategy, the methacrylamido derivative of FG was copolymerized by free radical initiation with different monomers, such as methyl methacrylate, glycidyl methacrylate, N‐tert‐butylacrylamide, methacrylic acid, N‐vinyl‐2‐pyrrolidinone, and vinyl acetate. Reaction of FG with preformed polymers containing epoxy groups generally afforded crosslinked materials. On the other hand, low FG loading extents were recorded by amidation of polymers containing carboxylic groups. Indeed, almost quantitative conversions were obtained only in the reaction of FG with anhydride containing polymers. The chemical structure, molecular weight properties, and the physical‐chemical characteristics of all synthesized polymeric dyes were thoroughly investigated. Some very preliminary dyeing tests of different cloth types with the prepared polymeric dyes were also performed.

UV absorption spectrum of poly(FGMAA) and poly(FGMAA‐co‐MMA) in chloroform at 25 °C (FGMAA = 4‐methacrylamido‐2′,3‐dimethylazobenzene).

magnified image

UV absorption spectrum of poly(FGMAA) and poly(FGMAA‐co‐MMA) in chloroform at 25 °C (FGMAA = 4‐methacrylamido‐2′,3‐dimethylazobenzene).
Impact Strength and Crystallization Behavior of Nano‐SiOx/Poly(phenylene sulfide) (PPS) Composites with Heat‐Treated PPS
Authors: Lu Dan , Mai Yiu‐Wing , Li Robert K. Y. , Ye Lin
Published: September 2003

The effects of heat treatment on the crystal structure and impact strength of poly(phenylene sulfide) (PPS) and nano‐SiOx/ PPS nanocomposites were studied. The molecular weight of heat‐treated neat PPS was increased by 28% due to the crosslinking reaction that changed its crystal morphology. Also, the crystallinity was reduced by 18%, leading to an improvement of the Izod impact strength by 66%. Nano‐SiOx/PPS composites were manufactured by intensive compounding with 3 wt.‐% nano‐SiOx particles treated by an epoxy functional group. Test results showed that the Izod impact strength of nano‐SiOx/heat‐treated PPS composites was 91% better and the crystallinity 27% less compared to the same properties of “as received” neat PPS. Nano‐SiOx has a high specific surface area and a high surface energy; its grafted epoxy group promotes interfacial adhesion with the PPS matrix, hence increasing the Izod impact strength of the nanocomposites.

TEM micrograph of NHTM‐PPS with 3 wt.‐% nano‐SiOx.

magnified image

TEM micrograph of NHTM‐PPS with 3 wt.‐% nano‐SiOx.
Promoting sustainable consumption: Determinants of green purchases by Swiss consumers
Authors: Tanner Carmen , Wölfing Kast Sybille
Published: September 2003

Given that overconsumption in industrial countries is a main cause of environmental degradation, a shift toward more sustainable consumption patterns is required. This study attempts to uncover personal and contextual barriers to consumers' purchases of green food and to strengthen knowledge about fostering green purchases. Survey data are used to examine the influence of distinct categories of personal factors (such as attitudes, personal norms, perceived behavior barriers, knowledge) and contextual factors (such as socioeconomic characteristics, living conditions, and store characteristics) on green purchases of Swiss consumers. Results from regression analysis suggest that green food purchases are facilitated by positive attitudes of consumers toward (a) environmental protection, (b) fair trade, (c) local products, and (d) availability of action‐related knowledge. In turn, green behavior is negatively associated with (e) perceived time barriers and (f) frequency of shopping in supermarkets. Surprisingly, green purchases are not significantly related to moral thinking, monetary barriers, or the socioeconomic characteristics of the consumers. Implications for policy makers and for companies and marketers engaged in the promotion and commercialization of green products are discussed. © 2003 Wiley Periodicals, Inc.
Relationship between product groups' price perceptions, shopper's basket size, and grocery store's overall store price image
Authors: Desai Kalpesh Kaushik , Talukdar Debabrata
Published: September 2003

This research investigates how consumers form an overall store price image (OSPI) of grocery stores. Whereas prior research on this topic has explored the influence of the number of products offered at lower prices and of the magnitude of such price reduction, this study addresses the following two questions: How do the (lower) prices offered on different types of products influence OSPI? Does such influence vary across consumers, and, if so, how? A general framework of product‐price saliency on consumers' OSPI is developed and tested. Specifically, based on two product‐related factors—consumption span (length of time required to finish the consumption of a standard unit of the product) and unit price, grocery‐store products are classified into four exhaustive and mutually exclusive product groups, and the relationship between OSPI and group‐level price perceptions across the four product groups is examined. The framework also examines to what extent this relationship is moderated by consumers' shopping‐basket size. Consistent with the proposed framework, this research finds strong empirical evidence of a systematic but differential relationship between OSPI and product group‐level price perceptions and also a systematic interaction effect with consumers' basket size. The findings help to identify focal product categories across distinct consumer segments and thus hold important strategic implications for category management and target marketing that are likely to increase the overall effectiveness of retail promotional strategies. © 2003 Wiley Periodicals, Inc.
Abelson tyrosine kinase is required to transduce midline repulsive cues
Authors: Hsouna Anita , Kim You‐Seung , VanBerkum Mark F.A.
Published: September 2003

Tyrosine phosphorylation‐dependent signaling cascades play key roles in determining the formation of an axon pathway. The cytoplasmic Abelson tyrosine kinase participate in several signaling pathways that orchestrate both growth cone advance and steering in response to guidance cues. Here, a genetic approach is used to evaluate the role for Abelson in growth cones during a decision to cross or not to cross the Drosophila embryonic midline. Our data indicate that both loss‐ and gain‐of‐function conditions for Abl cause neurons within the pCC/MP2 pathway to project across the midline incorrectly. The frequency of abnormal crossovers is enhanced by mutations in the genes encoding the midline repellent, Slit, or its receptor, Roundabout. In comm mutants, where repulsive signals remain elevated, increasing or decreasing Abl activity partially rescues commissure formation. Thus, both too much and too little Abl activity causes axons to cross the midline inappropriately, indicating that Abl plays a critical role in transducing midline repulsive cues. How Abl functions in this role is not yet clear, but we suggest that Abl may help regulate cytoskeletal dynamics underlying a growth cone's response to midline cues. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 15–30, 2003
Localization of ganglioside 9‐O‐acetyl GD3 in point contacts of neuronal growth cones
Authors: Negreiros Erika M. A. , Leão Ana C. M. , Santiago Marcelo F. , Mendez‐Otero Rosalia
Published: September 2003

Gangliosides are a large group of sialylated glycosphingolipids widely expressed in mammalian tissues. We have shown previously that the expression of 9‐O‐acetyl GD3 is highly correlated with periods of neurite outgrowth in the developing nervous system, and that the advance of dorsal root ganglia growth cones on laminin was halted in presence of an antibody specific for 9‐O‐acetyl GD3. In this work, we examined by immunocytochemistry and confocal microscopy whether this ganglioside is localized in point contacts in neuronal growth cones. We identified point contacts by immunoreactions with proteins, such as vinculin and β1 integrin, known to be associated with these structures in growth cones. Our observations indicate that 9‐O‐acetyl GD3 is specifically associated with vinculin and β1 integrin in point contacts of growth cones, suggesting a possible role for this particular ganglioside in the modulation of these contacts during neurite outgrowth. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 31–37, 2003