bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inland variability of carbon–nitrogen concentrations and δ13C in Amazon floodplain (várzea) vegetation and sediment
Authors: Martinelli Luiz A. , Victoria Reynaldo L. , de Camargo Plinio B. , Piccolo Marisa de Cassia , Mertes Leal , Richey Jeffrey E. , Devol Allan H. , Forsberg Bruce R. 
Published: April 2003

AbstractWe analysed carbon, nitrogen and δ13C values in sediment sampled in the Amazon floodplains. The surface sediment samples were collected along inland transects divided according to their vegetation cover: (a) forest, where the dominant vegetation was inundation forests; (b) grass, where the dominant vegetation was grasses, mainly from Echnochloa polystachya; (c) mixed, where the vegetation changed from grasses near the river bank to forest inland. The average sediment carbon and nitrogen concentrations were significantly higher in forest samples (C = 0·99%, N = 0·12%) than in grass samples (C = 0·84%, N = 0·10%). The average sediment δ13C was significantly heavier in grass (−26·7‰ ) than in forest samples (−28·6‰ ), reflecting the isotopically heavier C4 grasses carbon. In the forest and mixed transects inland, increases in the carbon and nitrogen concentrations were observed. At approximately 50 to 60 m from the riverbank, the concentration of carbon and nitrogen became similar to the river particulate organic carbon (POC) concentration, which is the primary floodplain sediment source. We hypothesized that this trend is caused by the deposition of carbon‐ and nitrogen‐depleted sand‐size particles in the first few metres of the floodplain, whereas the more enriched silt–clay particles are preferentially deposited far inland. In contrast to inland trends, no significant downriver trend was observed in the carbon and nitrogen concentrations. However, a downriver δ13C increase was observed for sediment in grass‐covered areas. Based on δ13C values in different várzea environments, we estimated the relative contribution of riverine POC and vegetation material present in the várzea sediments under different vegetation covers. For forest sediment samples we estimated that 60% of the carbon was derived from the riverine POC and the forests provided the remaining 40%. For open areas covered with grasses we estimated that only 10% was derived from these plants, and 90% was derived from riverine POC. Copyright © 2003 John Wiley & Sons, Ltd.
Nitrogen fixation and denitrification in a floodplain forest near Manaus, Brazil
Authors: Kreibich Heidi , Kern Jürgen 
Published: April 2003

AbstractThe Amazon floodplain (várzea) is seasonally affected by water level fluctuations of the Solimões/Amazon River. The drastic environmental changes that occur also include microbiological processes, such as nitrogen (N2) fixation and denitrification. Both processes were measured in the soil by the acetylene reduction assay and the acetylene block method in a várzea forest on Ilha de Marchantaria, Central Amazonia, Brazil. In the surface soil horizon (0–5 cm), N2fixation was highest during the exposed period (0·04–0·26 nmolN h−1g−1dry weight (dw)). In contrast, denitrification varied from 0 to 1·40 nmolN h−1g−1dw, with high rates during the submerged and the transition periods. No significant difference between locations with legume trees, with non‐legume trees and without trees could be observed. N2fixation rates of incubations (litter down to 450 cm depth) for samples collected during the exposed period ranged from 0 to 0·11 nmolN h−1g−1dw, with highest rates in the surface soil horizon (0–5 cm). Denitrification ranged from 0 to 0·05 nmolN h−1g−1dw, with the highest rate at 250–300 cm depth, which was just below the water table. The maximum N2fixation rate (0·89 nmolN h−1g−1dw) and denitrification rate (0·09 nmolN h−1g−1dw) occurred in the litter layer. On average, at least three times as much N is lost from the surface soil horizon via denitrification than is gained by N2fixation annually, but the rates are strongly influenced by the flood pulse. Copyright © 2003 John Wiley & Sons, Ltd.
Biogenic gas production from major Amazon reservoirs, Brazil
Authors: Rosa Luiz Pinguelli , Dos Santos Marco Aurelio , Matvienko Bohdan , Sikar Elisabeth , Lourenço Ronaldo Sérgio M. , Menezes Carlos Frederico 
Published: April 2003

AbstractMethane (CH4) and carbon dioxide (CO2) emissions from Brazilian reservoirs were assessed. Point measurements were made during 1998 and 1999 (using inverted funnels for bubbles and air and water concentration gradients for diffusion) in the 559 km2 Samuel reservoir, which was initially flooded in 1988, and the 2430 km2 Tucuruí reservoir, which was flooded in 1984, and the data were evaluated with respect to historical measurements in other Brazilian reservoirs. Bubble emissions of CH4 were higher in Samuel (ranging from 2 to 70 mgCH4 m−2 day−1) than in Tucuruí (ranging from 0·5 to 30 mgCH4 m−2 day−1), with the highest values occurring the shallowest regions in each reservoir. CH4 from diffusion for the Tucuruí reservoir ranged from 5 to 30 mgCH4 m−2 day−1, which is lower than that for the Samuel reservoir, which ranged from 10 to 80 mgCH4 m−2 day−1. The smaller emissions in Tucuruí compared with Samuel are attributed to a larger depletion in the source organic material that was present when the reservoir was filled. The CO2 concentration was similar for each reservoir, and ranged from 1000 to 10 000 mgCO2 m−2 day−1. Copyright © 2003 John Wiley & Sons, Ltd.
Does inequality cause conflict?
Authors: Cramer Christopher 
Published: April 2003

AbstractThis paper suggests that economic inequality is important to explaining civil conflict, but that the links are not as direct as is often supposed. It is important to focus on the variety of ways in which inequalities are managed by societies, and the significance of varying kinds of inequality. It is also important to understand the transmission mechanisms that enable a relatively peaceable durable inequality to turn into a violent conflict. These considerations, together with the poor quality of the available inequality data, should make us more cautious about the conclusions reached by cross‐country empirical studies into the causes of conflict which ascribe a strong predictive power to measures of inequality. Copyright © 2003 John Wiley & Sons, Ltd.
Buying peace or fuelling war: the role of corruption in armed conflicts
Authors: Le Billon Philippe 
Published: April 2003

AbstractAlthough corruption may have a corrosive effect on economies and rule‐based institutions, it also forms part of the fabric of social and political relationships. This endogenous character means that conflict may be engendered more by changes in the pattern of corruption than by the existence of corruption itself. Such changes, frequently associated with domestic or external shocks, can lead to armed conflict as increasingly violent forms of competitive corruption between factions ‘fuel war’ by rewarding belligerents. Controversially, ‘buying‐off’ belligerents can facilitate a transition to peace; but ‘sticks’ such as economic sanctions, rather than ‘carrots’, have dominated international conflict resolution instruments. While ‘buying peace’ can present a short‐term solution, the key challenge for peace‐building initiatives and fiscal reforms is to shift individual incentives and rewards away from the competition for immediate corrupt gains. This may be facilitated by placing public revenues under international supervision during peace processes. Copyright © 2003 John Wiley & Sons, Ltd.
Clans, cliques and captured states: rethinking ‘transition’ in Central and Eastern Europe and the former Soviet Union
Authors: Wedel Janine R. 
Published: April 2003

AbstractAn understanding of informal systems and of the ways in which they can shape political, economic and social institutions and processes is important in fashioning both systemic change and post‐conflict reconstruction strategies. In its absence attempts at reform are unlikely to have the intended effects. This paper distinguishes between the partially appropriated state and the clan‐state. The two models fall along a continuum—from substantial appropriation of the state and use of politics by private actors to sweeping appropriation and a near wholesale intertwining of state resources and politics. Both models are characterized by the negotiable status of informal groups, entities and institutions situated between state and private. Both may result in an expanded state sphere marked by ambiguity of status and responsibility. Copyright © 2003 John Wiley & Sons, Ltd.
The political economy of Zimbabwe's descent into conflict
Authors: Addison Tony , Laakso Liisa 
Published: April 2003

AbstractThe last two years have seen intensifying political violence in Zimbabwe. Could Zimbabwe slide further into political and economic turmoil? Or are there sufficient checks and balances in the social system to halt decline? The paper argues that the failed economic stabilization of the 1990s led to increased support for the opposition movement, especially among the middle‐class and trade unionists who were hit by high inflation. The veterans of the liberation war and peasants—who are the power base of the ruling party both ideologically and as voters—also became increasingly disgruntled as they had received very little after independence while the leadership had enriched itself. The government was able buy the loyalty of the war veterans and to use them to intimidate the opposition, although it does not have full control over their actions. The paper concludes that democratic forces within civil society can play an important role in conflict prevention and resolution by building bridges between the different dissatisfied groups. Copyright © 2003 John Wiley & Sons, Ltd.
Building institutions in post‐conflict African economies
Authors: Aron Janine 
Published: April 2003

AbstractInstitutions are altered by conflict, depending on the scale, duration and type of conflict. At one extreme, formal political, social and economic institutions may be completely destroyed (e.g. Somalia), while the importance and type of informal institutions may be changed. This survey addresses some of the current issues in the design and implementation of institution‐building and reform in sub‐Saharan Africa, and highlights the particular difficulties faced by post‐conflict countries. However, research on practical policy interventions toward institution‐building is still at an early stage. Copyright © 2003 John Wiley & Sons, Ltd.
Regional dimensions of conflict and peace‐building in contemporary Africa
Authors: Shaw Timothy M. 
Published: April 2003

AbstractAfrica's conflicts are diverse in their causes and consequences, and they are increasingly interrelated as well as regional in character. Their economic and non‐state features are undeniable, leading to some promising possibilities in terms of diplomacy, involving think tanks and NGOs in addition to formal institutions, both on and off the continent, such as the ‘Kimberley Process’ around ‘blood’ diamonds. Development corridors and trans‐frontier peace‐parks may also constitute innovative ways to moderate and contain conflict. As so often, changeable African cases challenge established assumptions, analyses and policies, such as those around civil society and governance as well as regional and security studies. Copyright © 2003 John Wiley & Sons, Ltd.
Organization‐internal transfer of knowledge and the role of motivation: a qualitative case study
Authors: Kalling Thomas 
Published: April 2003

AbstractThis paper reports a case study of a knowledge transfer programme in a manufacturing MNC, and suggests that firm‐internal knowledge transfer programmes are exercises requiring a great deal of recipient motivation. In contrast to existing theory, which has a tendency to address the role of cognitive factors such as tacitness, causal ambiguity and absorptive capacity, this paper suggests that motivation needs to be in place first. In the studied case, differences in local perceptions of transfer ventures, aspiration and strategic ambitions, internal competition, the view on the nature of knowledge and local communication seem to explain success and failure in transfer ventures. If motivation is not in place ‘naturally’, it can be managed in different ways, including local and corporate management control routines as well as organization structure. Consequently, we argue that knowledge transfer theory should not presume that organizational units are interested in the knowledge transferred, or that knowledge is always ‘good’. Knowledge is contextual, meaning it fits certain operations and strategies better, even in instances where intra‐organizational units are homogeneous. Hence motivation is central to transfer success. Copyright © 2003 John Wiley & Sons, Ltd.
Valuing of firms' prior knowledge: a measure of knowledge distance
Authors: Liyanage Shantha , Barnard Ross 
Published: April 2003

AbstractKnowledge, especially scientific and technological knowledge, grows according to knowledge trajectories and guideposts that make up the prior knowledge of an organization. We argue that these knowledge structures and their specific components lead to successful innovation. A firm's prior knowledge facilitates the absorption of new knowledge, thereby renewing a firm's systematic search, transfer and acquisition of knowledge and capabilities. In particular, the exponential growth in biotechnology is characterized by the convergence of disparate scientific and technological knowledge resources. This paper examines the shift from protein‐based to DNA‐based diagnostic technologies as an example, to quantify the value of a firm's prior knowledge using relative values of knowledge distance. The distance between core prior knowledge and the rate of transition from one knowledge system to another has been identified as a proxy for the value a firm's prior knowledge. The overall ‘difficulty of transition’ from one technology paradigm to another is discussed. We argue this transition is possible when the knowledge distance is minimal and the transition process has a correspondingly high value of absorptive capacities. Our findings show knowledge distance is a determinant of the feasibility, continuity and capture of scientific and technological knowledge. Copyright © 2003 John Wiley & Sons, Ltd.
Chain propagation rate constants for gas‐phase polymerization of propene and 1‐butene with Ziegler‐Natta catalysts
Authors: Oliva Leone , Di Serio Martino , Peduto Nicolangelo , Santacesaria Elio 
Published: April 2003

Abstract13C NMR analysis of propene/1‐butene block copolymers obtained by gas‐phase polymerization with Ziegler‐Natta catalysts allows the determination of the propagation rate constants for the homopolymerization of the two monomers. They are very similar for the Solvay type catalyst δ‐TiCl3/AlMe3 and the supported catalyst TiCl4/MgCl2/phthalate/AlMe3. The constant of propene polymerization is three times higher than that of 1‐butene polymerization. The high value of the constant found for propene polymerization is in agreement with the literature value determined by the stopped flow polymerization method.
Living cationic polymerization of cyclohexyl vinyl ether
Authors: Cramail Henri , Deffieux Alain 
Published: April 2003

AbstractThe cationic polymerization of cyclohexyl vinyl ether (CHVE) initiated by α‐halogeno ethers in the presence of a Lewis acid activator has been investigated first. In conditions leading to a living polymerization of alkyl vinyl ethers (ethyl, isobutyl, etc.), an extremely fast polymerization, accompanied by chain transfer reactions, is observed with CHVE. In fact, we have shown that the polymerization of this monomer may be directly initiated by the HI and HCl adducts of CHVE, in the absence of any electrophilic activator. However, even in these conditions, the polymerization cannot be controlled. A “living” polymerization of CHVE was finally obtained by addition of ammonium salts (NBu4X; X = Cl, Br, I) to the systems free of electrophilic activators. The added salts stabilize the α‐halogeno ether chain ends and reduce the overall reactivity. Using this procedure, we have synthesized poly(CHVE)s with M̄n's ranging from 6 · 103 to 4 · 104 g · mol−1 (in good agreement with the predicted values assuming the formation of one polymer chain per initiator molecule) and narrow molecular weight distributions (M̄w/M̄n < 1,2). Though most of poly(alkyl vinyl ether)s exhibit glass transition temperatures far below 0°C, the glass transition temperature of the poly(CHVE) is close to +50°C, indicating that this monomer can be used as a precursor to rigid poly(vinyl ether) blocks.
Free radical synthesis of α,ω‐primary amino functionalized polyisoprene through the functional thermal inferter [bis(N‐(2‐phthalimidoethyl)piperazine)]thiuram disulfide
Authors: Clouet Gilbert , Juhl Hans Jürgen 
Published: April 2003

AbstractThe primary amino functional iniferter [bis(N(2‐phthalimidoethyl)piperazine)]thiuram disulfide (PEPTD) was synthesied and characterized. Thermal polymerization of isoprene in the presence of the initiator afforded α,ω‐functionalized polyisoprene with primary amino end‐groups after cleavage of the phthalimido group with butylamine. The kinetics of polymerization of isoprene using this iniferter was studied at 80, 85, 90 and 100°C. Interestingly, isoprene showed a complex kinetic behavior. The different parameters, related to initiation, chain transfer and primary radical termination reactions, as well as the constants for thermal decomposition of the initiator, were determined. From the Arrhenius plot, the activation energy of the overall decomposition constant of PEPTD (2 f kd) was calculated to be 110 kJ/mol. The functionality of the telechelics was examined by GPC.
Polymorphism of poly[bis(p‐methoxyphenoxy)phosphazene]
Authors: Miyata Tadakazu , Masuko Toru , Kojima Morio , Magill Joseph H. 
Published: April 2003

AbstractWell characterized poly[bis(p‐methoxyphenoxy)phosphazene] (PB(4‐MeO)PP) has been investigated employing X‐ray diffraction and differential scanning calorimetry (DSC). The DSC heating scan of the original PB(4‐MeO)PP specimen exhibits one exotherm at 110°C and two endotherms at 106°C and 126°C, respectively. Only a single endotherm at 131°C appears on the second heating. X‐ray diffraction measurements at elevated temperature reveal that PB(4‐MeO)PP crystal is monoclinic (β‐form) with unit cell dimensions a = 2,47 nm, b = 1,98 nm, c = 0,983 nm and y = 102° in the range of 106–126°C. Initially PB(4‐MeO)PP specimens are observed to be orthorhombic (α‐form) with a = 2,39 nm, b = 1,79 nm and c = 0,983 nm. The crystal transforms at 106°C and then changes into the β‐form at 110°C according to DSC measurements. At 126°C the β‐form crystal changes into a mesophase with an intermolecular distance of 1,44 nm at 150°C. The 3‐dimensional orthorhombic γ‐form with a = 2,21 nm, b = 2,01 nm and c = 0,963 nm is found at room temperature after specimens are cooled through T(1) = 126°C from the mesophase.
Carbon 13 NMR study of oligo(propylene oxide)s
Authors: Le Borgne Alain , Moreau Michel , Vincens Valérie 
Published: April 2003

AbstractSamples of dimer and trimer derived from chiral propylene oxide, having head‐to‐tail linkages were prepared using an aluminium complex of a Schiff's base and were studied by means of 13C NMR spectroscopy. Based on these spectroscopic data and on J‐Modulated Spin Echo Technique (JMSET), analysis of a racemic oligomer (DPn ≈ 11) was carried out. Resonances of carbon atoms of central and terminal units were identified. End‐group carbon atoms (with the exception of CH2Cl) present large configurational effects as compared to internal carbon atoms.
Modeling of termination in intermediate and high conversion free radical polymerizations
Authors: Buback Michael , Huckestein Brigitta , Russell Gregory T. 
Published: April 2003

AbstractA simple means of modeling termination in free radical polymerizations of a large number of monomers over a wide variety of intermediate and high conversion conditions is presented. It is shown that monomers can be divided into two classes according to the qualitative variation of their termination rate coefficient (kt) with conversion (U). It is then suggested that it is profitable to represent kt data as kt/[kp·(1 − U)]. Doing this reveals that over a wide range of temperatures and of intermediate and high conversions, seemingly complex variations of kt with U can be described by a single parameter (CRD), the value of which varies from monomer to monomer. Proceeding from the idea that the process of reaction‐diffusion is the rate determining mechanism of termination, two easily implementable models for a priori prediction of CRD are developed in parallel from already existing ideas. One of these models is shown to predict with remarkable accuracy a large variety of experimental CRD data. Slight modification of these predictions makes this model even more accurate, and therefore gives it great potential for modeling purposes.
Block copolymers of poly(ether‐ether‐sulfones) with liquid‐crystalline/non‐liquid‐crystalline polyesters
Authors: Brenda Silviz , Heitz Walter , Karback Alexander , Wehrmann Rolf 
Published: April 2003

AbstractThe synthesis of telechellcs of poly(ether‐ether‐sulfones) (PEES) is controlled by high‐resolution gel‐permeation chromatography to optimize for low content of side products. Under optimum conditions the bifunctional polymer‐homologous series is formed to 99,9%. These telechrcs were used to synthesize block copolymers with aromatic polyesters. The polyesters (PE) contain phenylhdroquinone and terephthalic acid (semicrystalline liquid‐crystalline (LC) polyester), phenylterephthalic acid (amorphous LC polyester) or isophthalic acid (amorphous non‐LC polyester). Block copolymers with amorphous polyesters show one glass transition temperature depending on the composition but blends of corresponding homopolymers are biphase. Block copolymers with semicrystalline LC polyesters are phase‐separated. Incorporation of semicrystalline LC polyester segments into PEES increases their solvent resistance. The storage modulus of the block copolymer with 50 wt.‐% of the semicrystalline polyester shows the same temperature dependence as PEES. Homogeneous block copolymers show anisotropy only if the weight fraction of polyester is larger than 0,5 whereas phase‐separated systems show anisotropy at smaller fractions of polyester.
Synthesis of star‐shaped polydimethylsiloxanes containing SiO2 core units
Authors: Ogawa Takuya , Suzuki Toshio , Mita Itaru 
Published: April 2003

AbstractStar‐shaped polysiloxanes consisting of SiO2 cores and polydimethylsiloxane (PDMS) branches were successfully prepared by three methods using functionalized solvent‐soluble silicates as a starting material. The first method involved the lithiation of a SiOH functional silicate with butyllithium, followed by reaction with hexamethylcyclotrisiloxane (D3) and termination with a chlorosilane to afford a star polymer. In this case, the chain ends were substituted with vinyl or SiOH functional groups. In the second method, a SiCl functional silicate was used as the source of the SiO2 core. A PDMS chain with a lithium silanolate terminal group was reacted with the SiCl functional silicate to provide a star polymer. In the third method, a PDMS chain with a diethylamino group at one chain end was reacted with the SiOH functional silicate to form a star polymer. The Mark‐Houwink constant a of the star polymer was 0,74, which is very close to that of a linear PDMS.