bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Sequential Grain Marketing Decisions under Risk Aversion and Price Uncertainty
Authors: Blakeslee Leroy
Published: July 2006

A method is developed to find sequences of expected utility maximizing decisions under risk aversion when random elements are time‐dependent and additive separable utility of income is implausible. A Taylor‐series approximation to expected utility is used. In an application to marketing stored wheat, expected seasonal sales patterns, early fractional sales of total inventory for risk reduction, and negative skewness in resulting income distributions are noted. Sensitivity to the number of income distribution moments used to approximate expected utility is examined. Six moments produce a good approximation. Use of only mean and variance can give doubtful results.
What Causes Commodity Price Backwardation?
Authors: Frechette Darren L. , Fackler Paul L.
Published: July 2006

A recently proposed explanation for futures price backwardation is examined. An equilibrium model with spatial heterogeneity leads to the interpretation of backwardations as mismeasurement by the analyst. However, the model predicts that backwardations are more affected by the location of stocks than by their aggregate level. Empirical examination of the United States corn market fails to support this result.
Economic Feasibility of Variable‐Rate Technology for Nitrogen on Corn
Authors: Thrikawala Sunil , Weersink Alfons , Fox Glenn , Kachanoski Gary
Published: July 2006

The economic feasibility of three different fertilizer management strategies (constant rate, three‐rate and multiple‐rate technology) in the application of nitrogen fertilizer to corn are compared under different probability distributions for field fertility. A constant rate was more profitable than either variable‐rate technology system for homogeneous fields with low fertility. The application area at which the relative profitability between systems changed was largely determined by the characteristics of the fertility distribution rather than by assumptions regarding costs. Variable‐rate technology improves groundwater quality in low‐fertility fields by reducing total fertilizer applied and in high‐fertility fields by increasing corn yield.
Does Lack of Access to Formal Credit Constrain Agricultural Production? Evidence from the Land Tenancy Market in Rural India
Authors: Kochar Anjini
Published: July 2006

While it is commonly believed that lack of access to government‐subsidized “formal” credit underlies observed differences in farm productivity in rural India, there is little empirical evidence on this issue. In this paper I address this issue by examining whether households use the farm land rental market to equilibrate their access to formal credit, as they are known to do in the case of other imperfectly marketable inputs. This research reveals, however, that the advantage formal borrowers enjoy in the tenancy market does not reflect their access to formal credit per se, but their greater ownership of inputs such as irrigated land.
Discount Schedules and Grower Incentives in Grain Marketing
Authors: Hennessy David A. , Wahl Thomas I.
Published: July 2006

In this paper we develop a microeconomic optimization model of grain elevator cleaning and commingling decisions when the firm is faced with different discounting schedules. Using generalizations of Jensen's inequality, it is shown that a convex (concave) discount schedule encourages commingling (cleaning). However, a separate market for cleanings may qualitatively alter the optimal arrangement of grain. Wheat elevator records are studied to discern whether alternative discount schedules provide elevators with opportunities to cover the costs of rearranging grain composition. Rearrangement activities appear to be marginally profitable for some dockage levels.
Government Preferences and Public Forest Harvesting: A Second‐Best Approach
Authors: Amacher Gregory S.
Published: July 2006

Around the world governments own forest capital stocks and can harvest them for revenue or provide public goods from preserving them. This article examines how government preferences for revenue generation and public goods provision affect policy choices. Many instances are found where governments might exploit public forests at the expense of public goods. This is most likely when budget pressures are severe, or when the government prefers revenue generation to nontimber benefits provision. In particular, budget‐constrained governments are more likely to exploit public harvests to raise revenues and subsidize the forest sector, especially when revenues are increasing in public harvesting. Public harvesting should also influence tax choice. The results shed light on current forest policy debates and can be used to predict behavior of developed and developing country governments facing external pressures.
Integrator Contracts with Many Agents and Bankruptcy
Authors: Tsoulouhas Theofanis , Vukina Tomislav
Published: July 2006

This article analyzes optimal livestock production contracts between an integrator company and many independent growers in three similar industries: broiler, turkey, and swine. The analysis provides an explanation for the simultaneous existence of distinct incentive schemes in these industries by examining the effects of bankruptcy. The key factors are shown to be the output price volatility and the firm size. With large companies dominating the broiler industry, a small price volatility facilitates the use of two‐part piece rate tournaments. By contrast, given the prevalence of smaller companies in the swine industry, a larger price volatility generates a bankruptcy risk which renders the use of tournaments infeasible. Given the combination of medium‐size companies in the turkey industry, an intermediate price volatility produces a mixed result where tournaments and fixed performance standards exist simultaneously.
CVM‐X: Calibrating Contingent Values with Experimental Auction Markets
Authors: Fox John A. , Shogren Jason F. , Hayes Dermot J. , Kliebenstein James B.
Published: July 2006

We design and implement a method, CVM‐X, to calibrate hypothetical survey values using experimental auction markets. We test the procedure using consumer willingness‐to‐pay for irradiated/nonirradiated meat. Our results show that calibration factors for those who favor the irradiation process (0.67–0.69) are less severe than for those with an initial dislike of the process (0.55–0.59), suggesting that calibration may be commodity specific.
Bayesian Composite Qualitative Forecasting: Hog Prices Again
Authors: Dorfman Jeffrey H.
Published: July 2006

A new method for forming composite qualitative forecasts is presented. A set of qualitative forecasts is evaluated using auxiliary logit models to predict the probability of each forecast's correctness. Individual model forecasts are then combined on the basis of normalized values of these probabilities. This method is demonstrated with three sets of forecasts on the direction of change in hog prices (up or down). The application shows that without any information on the manner in which the individual forecasts are generated this method can form a composite forecast that is superior according to a variety of metrics for evaluating qualitative forecasts.
Marketing Agreement Impacts in an Experimental Market for Fed Cattle
Authors: Ward Clement E. , Peel Derrell S. , Trapp James N. , Dowty Tracy L. , Koontz Stephen R.
Published: July 2006

Marketing agreements between meatpacking and cattle feeding firms have created concerns about their effects on fed cattle prices. Profit‐sharing marketing agreements were imposed onto a simulated fed cattle market. Price level and variability differences with and without agreements, between agreement participants and nonparticipants, during agreement and nonagreement periods, and between participants receiving and not receiving a monetary incentive were evaluated. Prices and variability for nonagreement cattle were higher during the agreement periods. Marketing agreement participants realized lower, less variable prices than nonparticipating firms. Monetary incentives did not affect price levels but increased price variability.
Testing Theories of Consumption Behavior Using Information on Aggregate Shocks: Income Seasonality and Rainfall in Rural India
Authors: Jacoby Hanan G. , Skoufias Emmanuel
Published: July 2006

We develop an integrated framework for testing theories of consumption behavior by examining how agricultural households in rural India respond to anticipated and unanticipated seasonal income fluctuations. Using information on village‐level rainfall surprises, we estimate idiosyncratic unanticipated income shocks by allowing weather risk to impact households differently depending on observable characteristics. In applying our methodology to unique panel data on consumption, debt, and intrahousehold gift exchanges, we address a number of shortcomings in previous tests of theories of consumption behavior. Yet, we find no evidence against the hypothesis that households smooth idiosyncratic fluctuations in their income. Our approach also uncovers several interesting features of rural credit and insurance markets.
Individual and Household Willingness to Pay for Public Goods
Authors: Quiggin John
Published: July 2006

The issue of whether willingness to pay (WTP) for the benefits generated by a public good should be elicited on an individual or on a household basis is addressed. Differences between individual and household WTP may arise when members of the household are mutually altruistic. It is shown that, for general specifications of altruism, household WTP is less than the sum of household members' individual WTP. Implications for the choice between household and individual measures of WTP are considered, and issues in the elicitation of household WTP are addressed.
Needed Redirections in Economic Analysis for Agricultural Development Policy
Authors: Dorner Peter
Published: July 2006

Economic literature identifies development with average rates of increase in real output per capita. Little research has focused on interrelations between productivity increases and other indicators of development such as the reduction of mass poverty, unemployment, and inequality. Such omissions may be a function of the way agricultural economics developed in the United States. Here a positive correlation between increased production, employment, and income‐earning opportunities was assumed inherent in the family farm system and the relative labor‐scarce conditions. Problems emerging in recent years throw considerable doubt on the appropriateness of these assumptions.
Formulating Beef Rations for Improved Performance under Environmental Stress
Authors: Brokken Ray F.
Published: July 2006

Beef ration heat increment level (energy lost in ruminant fermentation and nutrient metabolism) relative to net energy has important implications for efficient beef production under heat or chill stress. This paper presents (1) an efficient model for use of the Lofgreen‐Garrett net energy system in ration formulation; (2 ) a model, incorporating the Lofgreen‐Garrett net energy system, for varying heat increment relative to net energy in beef ration formulation; and ( 3) a simplified framework for ascertaining potential animal performance differences caused by differences in relative heat increment under assumed stress conditions. Differences illustrated are substantial.
Identity game: Czech and Slovak architecture magazines as travelogues
Authors: Topolcanska Maria
Published: June 2006

Meanings inevitably shift with the point of view of the commentator. Maria Topolcanska investigates the shifting identities of Czech and Slovak architectures over time, from the postwar era through to the present. Creating an analogy between the historic travelogues of the past and the assumptions of the Western media, she emphasises the need for local architectures to be disseminated through locally organised platforms and press. Copyright © 2006 John Wiley & Sons, Ltd.
Slovenia: an architectural heritage moving forward
Authors: Hrausky Andrej
Published: June 2006

Slovenia has a rich history of Modern architecture. Its capital, Ljubljana, is well known for the distinctive buildings of Joze Plecnik as well as those of the Secessionist and Functionalist eras. Since opening up to the West in the early 1990s, a younger generation of Slovene architects has been propelled to the fore, who have been able to benefit from the advantages of exposure to international teaching and ideas. Andrej Hrausky describes the historical and national context in which contemporary Slovene architects work and asks how their output might relate to it in the future. Copyright © 2006 John Wiley & Sons, Ltd.
Estonia: the remarkable afterlife of the Linnahall concert hall
Authors: Kurg Andres
Published: June 2006

Built in 1980, the Linnahall Concert Hall in Tallinn, Estonia, is a fairly recent but nonetheless controversial Soviet monument. Having been highly praised on its completion for its bold architectural solution, within a decade its close associations with the previous regime meant that it had fallen into disrepute. Developers, who realised the economic potential of the site, were quick to seize on its controversial history and called for its destruction. Andres Kurg looks at the changing role of the Linnahall in Tallinn over time and asks what the future might now hold for it. Copyright © 2006 John Wiley & Sons, Ltd.
Poland: transforming factories into cultural and educational facilities
Authors: Trammer Hubert
Published: June 2006

Architecture has an important role to play in the refurbishment and renovation of existing building stock, often leading to the wholesale regeneration of run‐down and derelict areas. Hubert Trammer looks at how the redevelopment of five disused industrial sites in Poland has been driven by the need for new educational and cultural facilities and the widespread availability of abandoned manufacturing bases. Copyright © 2006 John Wiley & Sons, Ltd.
Integrated Approach for the Development of Advanced, Coated Gas Turbine Blades
Authors: Herzog R. , Warnken N. , Steinbach I. , Hallstedt B. , Walter C. , Müller J. , Hajas D. , Münstermann E. , Schneider J. M. , Nickel R. , Parkot D. , Bobzin K. , Lugscheider E. , Bednarz P. , Trunova O. , Singheiser L.
Published: June 2006

This paper describes a through‐process modelling on a microstructural level of the production of a coated turbine blade, including its in‐service properties and degradation, accompanied by the actual production and testing of a CMSX‐4 single crystal turbine blade dummy. The following steps are dealt with by modelling and experiment: solidification of the blade alloy during casting, microstructural changes during homogenization and aging heat treatments, chemical vapour deposition of an Al2O3diffusion barrier coating, physical vapour deposition (sputtering) of a (Ni,Co)CrAlY bond coat, atmospheric plasma spraying of an Y2O3stabilized ZrO2thermal barrier coating and microstructural changes and development of critical stresses at in‐service conditions. This work forms a part of the Collaborative Research Centre 370 (SFB 370) “Integrative materials modelling”.
Control over Cement Setting Through the Use of Chemically Modified Fly Ash
Authors: Lupu C. , Jackson K. L. , Bard S. , Rusakova I. , Barron A. R.
Published: June 2006

The chemical treatment of Class C fly ash with a 0.2 wt% of CaCO3 solution results in dramatic increase in setting time and superior stability during the induction period for cement slurries at temperature conditions relevant for down‐hole applications. The performance of the CaCO3 treatment appears to be a consequence of each fly ash particle being provided with the necessary Ca prior to hydration without being dependant on cement‐fly ash particle interactions. Thus, the setting process is no longer dependent on the particle shape, packing and dispersion of the fly ash and cement. That with the extended setting times, the induction period follows almost ideal shape is most important for oil well applications where it is necessary to pump a specific viscosity slurry over large distances within a specific time, without changes in viscosity that would effect pump rates.
2D and 3D Visualization of Ductile Fracture
Authors: Weck A. , Wilkinson D. S. , Toda H. , Maire E.
Published: June 2006

New model materials made of laser drilled copper sheets have been fabricated to study the ductile fracture process. In‐situ tensile tests in a scanning electron microscope and in an X‐Ray computed tomography set‐up allows us to observe the void growth and coalescence in 2D and 3D. It is shown that there are different modes of coalescence depending on the voids geometry and that constraining effects in the 3D case allow more void growth prior coalescence.
3‐D Image‐Based Mechanical Simulation of Aluminium Foams: Effects of Internal Microstructure
Authors: Toda H. , Takata M. , Ohgaki T. , Kobayashi M. , Kobayashi T. , Uesugi K. , Makii K. , Aruga Y.
Published: June 2006

SR (Synchrotron radiation) X‐ray microtomography has been utilized for the 3D characterization of microstructures in an aluminium foam. Volume tomographic data sets are converted into stereolithography tessellation language (STL) models to create 3‐D finite‐element simulation models. Both quasi‐static and dynamic deformation and damage behaviours are investigated numerically, especially focussing on the effects of relatively small micro‐pores inside cell wall materials. It has been fairly obvious that the existence of micro‐pores and their spatial distribution pattern in cell materials would be a key issue to control the deformation and fracture behaviours. It has been also clarified that the stress wave propagation during the dynamic loading is prone to relatively uniform local stress elevation compared to the case of the static compression, thereby more extensive damage is predicted in the case of the dynamic loading due to the increase in volume sampled by an external loading. These results are in qualitative agreement with experimental observations. Overall, the approach taken in this study has provided highly effective ways to characterize microstructure/properties relationships in such highly heterogeneous materials.
Mean Field and Multiscale Modeling of a Particle Reinforced Metal‐Matrix Composite Based on Microtomographic Investigations
Authors: Kenesei P. , Klohn A. , Biermann H. , Borbély A.
Published: June 2006

Based on evaluations of 3‐D X‐ray microtomographic reconstructions simple mean‐field and multi‐scale models were developed for predicting the plastic response of particle reinforced metal‐matrix composites. It is shown that increasing heterogeneity, by taking more details of the microstructure into account, leads to stress‐strain curves, which differ only slightly from the curve of the mean‐field model.
X‐ray Microtomographic Characterisation of Porosity and its Influence on Fatigue Crack Growth
Authors: Li P. , Lee P. D. , Lindley T. C. , Maijer D. M. , Davis G. R. , Elliott J. C.
Published: June 2006

Cast Al alloys are seeing increasing use in transport applications due to their high strength‐to‐weight ratio at an acceptable cost compared to many ferrous alloys. Therefore, a quantitative characterisation of the pore distribution and its influence on the evolution of fatigue damage are required to predict the fatigue life of cast Al alloy components. In this investigation, X‐ray microtomography was used to characterise the 3D morphology of porosity in A356‐T6 specimens and to relate the porosity to fatigue behaviour.
X‐ray Microtomography Analysis of Dynamic Damage in Tantalum
Authors: Bontaz‐Carion J. , Pellegrini Y.‐P.
Published: June 2006

With the plate‐impact technique, ductile spallation experiments are carried out on Ta at impact velocities 570, 1039 and 1078 m/s. Samples are soft‐recovered and analyzed by X‐Ray microtomography at the European Synchrotron Radiation Facility. The porosity along the shock direction, and the distribution of the pore volumes are extracted from tri‐dimensional reconstructions of the damaged samples. Quantitative assessment of pore coalescence is made via an inverse power‐law model for the distribution. The decay exponent we associate to coalescence is of order 1.6 in the sample impacted at 1039 m/s.
Validation of Marker Material Flow in 4mm Thick Friction Stir Welded Al 2024‐T351 through Computer Microtomography and dedicated Metallographic Techniques
Authors: Zettler R. , Donath T. , dos Santos J. F. , Beckman F. , Lohwasser D.
Published: June 2006

This study forms part of a joint three year project between the GKSS‐Forschungszentrum and Airbus Deutschland titled “Effect of material flow patterns on the properties of friction stir welds in aluminium alloys for aircraft structures” ‐EMFASIS. The global aim of our research project is to identify how process and geometric parameters such as weld tool geometry influence the weld energy and subsequent joint properties of four friction stir welded aerospace grade aluminium alloys. The current study reports on the visualisation and displacement of a Ti powder marker material dispersed within the weld zone and investigated with the aid of X‐ray computer microtomography (μCT) and dedicated metallographic techniques.
Cover Picture: The Role of Oxidation During Compaction on the Expansion and Stability of Al Foams Made Via a PM Route (Adv. Eng. Mater. 6/2006)
Authors: Asavavisithchai S. , Kennedy A. R.
Published: June 2006

The foam expansion and collapse behaviour for hot compacted Al‐TiH2 precursors has been shown to be driven by the oxidation of the Al powder and the premature loss of gas from the TiH2 foaming agent during the compaction process. At 550 °C, oxidation is rapid, and gas loss from the hydride is extensive leading to poor expansion.
Dioxouranium(VI) – Carboxylate Complexes. Interaction with Dicarboxylic Acids in Alqueous Solution: Speciation and Structure
Authors: Berto Silvia , Crea Francesco , Daniele Pier G. , de Stefano Concetta , Prenesti Enrico , Sammartano Silvio
Published: June 2006

In this paper we report the results of an investigation performed by potentiometric (H+‐glass electrode) and visible spectrophotometric measurements on the interaction of UO22+ ion towards some carboxylic ligands (acetate, malonate, succinate, azelate). The measurements were carried out at T = 25 °C in different ionic media (KNO3 and NaCl) at different ionic strengths (0.1 ≤ I/mol L‐1 ≤ 1.0, NaCl; I/mol L‐1 = 0.1, KNO3). The dependence on ionic strength of formation constants was taken into account by using both a simple Debye‐Hückel type equation and the SIT (Specific ion Interaction Theory) approach. Different speciation models (depending on concentration of reagents, ionic strength, pH‐range) both for different carboxylates and different ionic media have been obtained. Linear combinations between formation constants, stoichiometric coefficients and length of alkyl chain of dicarboxylates have been observed and predicted formation constants at I = 0 mol L‐1 are reported for the interaction of UO22+ with HOOC‐(CH2)n‐COOH with 1 ≤ n ≤ 7. Finally, a visible absorption spectrum for each complex reaching a significant percentage of formation in solution (KNO3 medium) has been calculated to characterise the compounds found by pH‐metric refinement.
A Highly Selective Spectrophotometric Determination of Niobium (V) Using 3‐Hydroxy‐2‐[1'‐Phenyl‐3'‐(p‐Chlorophenyl)‐4′‐Pyrazolyl]‐4‐Oxo‐4H‐1‐Benzopyran as a Complexing Agent
Authors: Agnihotri Nivedita , KAMAL Raj , MEHTA Jaswant R.
Published: June 2006

3‐Hydroxy‐2‐[1'‐phenyl‐3'‐(p‐chlorophenyl)‐4'‐pyrazolyl]‐4‐oxo‐4H‐1‐benzopyran(HPCPB) is used as an analytical reagent for the spectrophotometric determination of niobium in trace amounts with which it forms a yellow coloured complex (4:1) in perchloric acid medium. The complex is extractable into chloroform and shows absorption maximum at 407‐418 nm with a molar absorptivity of 2.79 × 104 L mol‐1 cm‐1 and Sandell's sensitivity equal to 0.0033 μg Nb(V) cm‐2 , respectively. Beer's law holds good in the range 0‐1.2 μg Nb ml‐1, with a standard deviation of ± 0.0015 absorbance units. The method is free from the interference of a large number of elements and handles satisfactorily the analysis of various samples of varying complexity.
Senio River Ecosystem: Characterization and Distribution of Inorganic Species in Water and Sediments
Authors: Melucci Dora , Torsi Giancarlo , Locatelli Clinio
Published: June 2006

Analytical results are reported for the determination of inorganic species in water and sediments sampled in the Senio river ecosystem. The species determined are Cu, Pb, Cd, Zn, Co, Cr, Ni, Fe, Mn, Hg, F‐, Cl‐, Br‐, NO3‐, SO4‐‐, Na+, K+, Ca++, Mg++, NH4+ in integrated water, and Cu, Pb, Cd, Zn, Co, Cr, Ni, Fe, Mn, Hg in sediments. For all the elements, in addition to detection limits, precision and accuracy are given: the former, expressed as relative standard deviation (sr), and the latter, expressed as relative error (e), were good, being in all cases lower than 6 %.

Limitedly to Cu, Pb, Cd and Zn a critical comparison with voltammetric measurements is also discussed.
Nickel(0)/Imidazolium Carbene Catalyst System for Efficient Cross‐Coupling of Aryl Bromides and Chlorides with Organomanganese Reagents
Authors: Leleu Anne , Fort Yves , Schneider Raphaël
Published: June 2006

N,N′‐Bis(2,6‐diisopropylphenyl)imidazolium chloride associated with nickel(II) acetylacetonate (3–5 mol %) was used as catalyst to efficiently cross‐couple functionalized aryl bromides with organomanganese reagents. The reactions were performed between 0 °C and room temperature, giving unsymmetrical biaryls in 0.25 to 24 h with 52 to 100 % yields for isolated materials. Aryl chlorides showed slightly diminished reactivity in Ni/2 IPr‐catalyzed cross‐couplings and good yields could only be attained with activated or neutral substrates.
Asymmetric Epoxidation of Olefins by Manganese(III) Complexes Stabilised on Nanocrystalline Magnesium Oxide
Authors: Choudary B. M. , Pal Ujjwal , Kantam M. Lakshmi , Ranganath K. V. S. , Sreedhar B.
Published: June 2006

The asymmetric epoxidation of unfunctionalised olefins to epoxides is realised by using manganese(III) complexes stabilised on nanocrystalline magnesium oxide in the presence (1R,2R)‐(−)‐diaminocyclohexane as a chiral ligand in good yields and up to 91 % enantiomeric excess.
Enhancement of Reaction Rates by Segmented Fluid Flow in Capillary Scale Reactors
Authors: Ahmed Batoul , Barrow David , Wirth Thomas
Published: June 2006

For a simple biphasic hydrolysis, we show that the application of various reaction conditions in microreactors using segmented flow can dramatically increase the reaction rate. A tandem diazotation/Heck reaction served as an example that even homogeneous reactions can be accelerated by segmentation in microreactors.
A New Metal‐Free Access to Vitamin K3
Authors: Bohle Anne , Schubert Anett , Sun Yu , Thiel Werner R.
Published: June 2006

2‐Methylnaphthalene is oxidized in about 80 % yield with 7–9/1 regioselectivity to 2‐methyl‐1,4‐naphthoquinone by hydrogen peroxide with a strong mineral acid as the catalyst. No (transition) metal catalyst is required for this transformation.
Redox‐Switchable Phase Tags – Facile Mitsunobu Reactions using Ferrocenyl‐Tagged Triphenylphosphine
Authors: Fleckenstein Christoph A. , Plenio Herbert
Published: June 2006

The use of redox‐switched phase tags in ferrocenyl‐substituted triphenylphosphine combined with DBAD (di‐tert‐butyl azodicarboxylate) allows high yield (>90 %) Mitsunobu transformations without the need for the chromatographic purification of the products. The redox‐switchable phosphine can be easily synthesized in two steps from 4‐bromoaniline, ferrocene and chlorodiphenylphosphine. It is separated from the reaction mixture by oxidation with iron(III) chloride and can be recycled efficiently by reductive treatment.
Development of a Method for Preparing a Highly Reactive and Stable, Recyclable and Environmentally Benign Organopalladium Catalyst Supported on Sulfur‐Terminated Gallium Arsenide(001): A Three‐Component Catalyst, {Pd}‐S‐GaAs(001), and its Properties
Authors: Arisawa Mitsuhiro , Hamada Masahiro , Takamiya Ikuko , Shimoda Masahiko , Tsukamoto Shiro , Arakawa Yasuhiko , Nishida Atsushi
Published: June 2006

We have developed a method for preparing a recyclable and environmentally benign organopalladium catalyst for the Heck reaction supported on sulfur‐terminated gallium arsenide(001). This three‐component catalyst, {Pd}‐S‐GaAs(001), exhibited high stability and activity, furthermore, it tolerated reuse in 10 runs of the Heck reaction (average yield, 97 %) under aerobic conditions. The sulfur layer was very important to stabilize this catalyst. Only trace amounts of Pd were leached from this catalyst to the reaction mixture, as measured by ICP‐mass. The valence of immobilized Pd was zero by XPS spectrometry.
Efficient and Selective Rhodium‐Catalyzed Hydrophosphorylation of Dienes
Authors: Ajellal Noureddine , Thomas Christophe M. , Carpentier Jean‐François
Published: June 2006

The hydrophosphorylation of a model 1,6‐diene having a terminal and an internal alkene function has been investigated. Free radical protocols lead invariably to mixtures of cyclic phosphonate products, due to rapid cyclization of the intermediary radical species. Rhodium catalysis using a cyclic pinacol‐derived phosphonate provides an efficient technique for the highly selective (>99 %) hydrophosphorylation at the terminal alkene function. In situ modification of Wilkinson’s complex by addition of 2–50 equivalents (vs. Rh) of a monophosphine (PCy3>PPh3) or carbene ligand greatly improves the catalyst performances (TON up to 2250 mol phosphonate/mol Rh). An even more efficient system was obtained with 2 equivalents (vs. Rh) of the bidentate 1,6‐bis(diphenylphosphino)hexane ligand, which affords so far unprecedented high catalytic productivity (TON up to 4 550 mol phosphonate/mol Rh) and activity (TOF up to 250 h−1).
Synergistic Effect of a Palladium‐on‐Carbon/Platinum‐on‐Carbon Mixed Catalyst in Hydrogen/Deuterium Exchange Reactions of Alkyl‐Substituted Aromatic Compounds
Authors: Ito Nobuhiro , Watahiki Tsutomu , Maesawa Tsuneaki , Maegawa Tomohiro , Sajiki Hironao
Published: June 2006

We have found a synergistic effect in the H‐D exchange reaction of alkyl‐substituted aromatic compounds using the Pd/C‐Pt/C‐D2O‐H2 system. This system would lead to fully H‐D exchange results even on the sterically hindered sites which were only low‐deuterium incorporated by Pd/C or Pt/C independently. Since the reaction was general for a variety of aromatic compounds, it could be applied to the deuteration of dianiline derivatives as raw materials for polyimides.
Zinc‐Catalyzed Enantioselective Hydrosilylation of Imines
Authors: Park Bu‐Mahn , Mun Soungyun , Yun Jaesook
Published: June 2006

The highly enantioselective reduction of imines is achieved by employing chiral Zn/diamine catalysts. This new catalytic protocol offers attractive features such as use of a non‐precious metal and an inexpensive silane, easy modification of chiral diamine ligands and provides ready access to chiral amines in good yields and with excellent enantioselectivities.
Cover Picture: Formation of Self‐Organized Dynamic Structure Patterns of Barium Carbonate Crystals in Polymer‐Controlled Crystallization (Angew. Chem. Int. Ed. 27/2006)
Authors: Wang Tongxin , Xu An‐Wu , Cölfen Helmut
Published: June 2006

The Belousov–Zhabotinsky reaction with its typical concentric ring pattern is described for a precipitation for the first time by T. Wang, A.‐W. Xu, and H. Cölfen in their Communication on page 4451 ff. The formation and self‐organization of BaCO3 nanoparticles can be directed with a new phosphonated block copolymer: short to ultralong nanofibers and, ultimately, ring patterns are obtained. This system could help to explain natural pattern formation. The cover picture shows observed and simulated Belousov–Zhabotinsky ring patterns, as well as the molecular structure of the block copolymer.
Polymeric proton conducting systems based on commercial elastomers. III. Microstructural and electrical characterization of films based on HSBS/EPDM/PP/PS/silica
Authors: Escribano P. G. , Nacher A. , Del Río C. , González L. , Acosta J. L.
Published: June 2006

This study goes on with the microstructural and electrical characterization of the films, object of our study, containing hydrogenated poly(butadiene‐styrene) block copolymer (HSBS). Ethylene–propylene terpolymer (EPDM), and a third component, polypropylene (PP), polystyrene (PS), or silica, crosslinked with peroxides and heterogeneously sulfonated. This process pursues the obtaining of materials with high proton conductivity and great dimensional stability, suited for application in a variety of electronic devices. The structural characterization consists of the study of the dynamic mechanical properties of all the samples, before and after the sulfonation, and also the checking of their structure by infrared spectroscopy. The analysis of the electrical properties of the films hydrated is achieved by electrochemical impedance spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 13–21, 2006
Moisture sorption and thermal characteristics of polyaramide blend fabrics
Authors: Genç Gözde , Alp Burcu , Balköse Devrim , Ülkü Semra , Cireli Aysun
Published: June 2006

Four types of fabrics woven from various polyaramid fibers of Nomex and Kevlar blends were characterized by morphology, XRD, elemental analysis, thermal analysis, and moisture adsorption isotherms. The blends consisted of Polybenzimidazole/Kevlar blend (40% PBI and 60% Kevlar®), Nomex Delta A (blend of 60% Kevlar and 40% Nomex®), Nomex Delta T (blend of 75% Nomex, 23% Kevlar, and 2% P140 antistatic fiber), and Nomex III (fabric with a 95/5 blend of Nomex and Kevlar) containing 1% steel fiber. TGA and DTG curves have been compared to evaluate thermal behavior of the PBI, Kevlar, and Nomex blends and the resuls were correlated with the moisture sorption data. The data were also compared with fiber morphologies provided by SEM and crystallinities derived from XRD diffractograms. Moisture adsorption isotherms were correlated with a number of empirical models, including Nernst, Freundlich, Handersen, Iglesias‐Chirife, and with the models having a theoretical background such as Langmuir, BET, GAB, and Hüttig. The linear regression models were statistically analyzed to obtain the best fitting model that explains the sorption profiles of the samples and theoretical monolayer moisture capacities of Nomex and Kevlar blends were calculated by using Hüttig isotherms. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 29–38, 2006
Ordering in a glycine‐rich peptide conjugate: Microscopic, fluorescence, and metalation studies
Authors: Prasad K. Krishna , Verma Sandeep
Published: June 2006

Glycine residues play an intriguing role in peptide/protein structure where they can act as tightly packing amino acids with flexible bond angles. For example, structural role of glycines is highlighted in natural silk fibers where different structural polymorphs have been reported. This study deals with a glycine‐rich segment from the conserved octarepeat (PHGGGWGQ) in prion protein. We have synthesized a bis‐conjugate 3, containing a truncated pentapeptide segment (GGGWG), to study its time‐dependent solution phase aggregation by a combination of microscopic methods and fluorescence. This discontinuous peptide conjugate 3 exhibited interesting photophysical properties upon self‐assembly allowing us to propose a possible model of peptide filament formation. Taking note of the fact that prion octarepeats bind copper, we also demonstrate the ability of this conjugate to bind copper and the growth and ultrastructure of metallized fibers formed upon incubation. Enforcing peptide fiber formation in metal binding motifs offers an entry into metal impregnated fibers for possible nanobiotechnological applications. © 2006 Wiley Periodicals, Inc. Biopolymers 83:289–296, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Influence of point mutations on the flexibility of cytochrome b5: Molecular dynamics simulations of holoproteins
Authors: Cheng Qinyi , Benson David R. , Rivera Mario , Kuczera Krzysztof
Published: June 2006

Two membrane‐bound isoforms of cytochrome b5 have been identified in mammals, one associated with the outer mitochondrial membrane (OM b5) and the other with the endoplasmic reticulum (microsomal, or Mc b5). The soluble heme binding domains of OM and Mc b5 have highly similar three‐dimensional structures but differ significantly in physical properties, with OM b5 exhibiting higher stability due to stronger heme association. In this study, we present results of 8.5‐ns length molecular dynamics simulations for rat Mc b5, bovine Mc b5, and rat OM b5, as well as for two rat OM b5 mutants that were anticipated to exhibit properties intermediate between those of rat OM b5 and the two Mc proteins: the A18S/I32L/L47R triple mutant (OM3M) and the A18S/I25L/I32L/L47R/L71S quintuple mutant (OM5M). Analysis of the structure, fluctuations, and interactions showed that the five b5 variants used in this study differed in organization of their molecular surfaces and heme binding cores in a way that could be used to explain certain experimentally observed physical differences. Overall, our simulations provided qualitative microscopic explanations of many of the differences in physical properties between OM and Mc b5 and two mutants in terms of localized changes in structure and flexibility. They also reveal that opening of a surface cleft between hydrophobic cores 1 and 2 in bovine Mc b5, observed in two previously reported simulations (E. M. Storch and V. Daggett, Biochemistry, 1995, Vol. 34, pp. 9682–9693; A. Altuve, Biochemistry, 2001, Vol. 40, pp. 9469–9483), probably resulted from removal of crystal contacts and likely does not occur on the nanosecond time scale. Finally, the MD simulations of OM5M b5 verify that stability and dynamic properties of cytochrome b5 are remarkably resistant to mutations that dramatically alter the stability and structure of the apoprotein. © 2006 Wiley Periodicals, Inc. Biopolymers 83:297–312, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Crystallization of IgG1 by mapping its liquid–liquid phase separation curves
Authors: Jion Adam Idu , Goh Lin‐Tang , Oh Steve K.W.
Published: June 2006

Monoclonal antibody therapeutics is an important and fast expanding market. While production of these molecules has been a major area of research, much less is known regarding the stabilization of these proteins for delivery as drugs. Crystallization of antibodies is one such promising route for protein stabilization at high titers, and here we took a systematic approach to initiate crystallization through nucleation in a simple PEG (polyethylene glycol), protein in water solution. A ternary mixture of globular proteins, PEG, and water will undergo a liquid–liquid phase separation (LLPS) as shown in a phase diagram or a Binodal curve. Of particular interest within the phase diagram is the position of the critical point, which is where nucleation occurs most rapidly. Detailed LLPS maps were created by increasing concentrations of PEG (from 5% to 11%) and IgG (from 1 to 20 mg/mL). By increasing the molecular weight (MW) of PEG (and hence its radius of gyration) from 1,000 to 6,000 g/mol, the temperatures of the critical point of nucleation were shown to increase. Once these curves were determined, nucleation experiments were conducted close to a chosen critical point (10.5 mg/mL IgG in 11% PEG 1000) and after 3 weeks, crystals of IgG of approximately 100 μm in size were successfully formed. This is the first example of crystallization of an antibody through systematic mapping of LLPS curves, which is a fundamental step towards the scale‐up of antibody crystallization. © 2006 Wiley Periodicals, Inc.
Long‐Lived Palladium Catalysts for CO/Vinyl Arene Polyketones Synthesis: A Solution to Deactivation Problems
Authors: Durand Jérôme , Zangrando Ennio , Stener Mauro , Fronzoni Giovanna , Carfagna Carla , Binotti Barbara , Kamer Paul C. J. , Müller Christian , Caporali Maria , van Leeuwen Piet W. N. M. , Vogt Dieter , Milani Barbara
Published: June 2006

A series of cationic palladium complexes of general formula [Pd(Me)(MeCN)(N–N)][PF6] (N–N = (phen) 1 a, 4,7‐dichloro‐1,10‐phenanthroline (4,7‐Cl2‐phen) 2 a, 4,7‐diphenyl‐1,10‐phenanthroline (4,7‐Ph2‐phen) 3 a, 4‐methyl‐1,10‐phenanthroline (4‐Me‐phen) 4 a, 4,7‐dimethyl‐1,10‐phenanthroline (4,7‐Me2‐phen) 5 a, 5,5,6,6‐tetrafluoro‐5,6‐dihydro‐1,10‐phenanthroline (F4‐phen) 6 a, containing different substituted phenanthroline ligands, have been prepared from the corresponding neutral chloro derivatives [Pd(Me)(Cl)(N–N)], (1 b–6 b). The X‐ray crystal structure of [Pd(Cl)2(4,7‐Cl2‐phen)] (2 b′) was determined. DFT calculations show that the electron density on the metal is tuned by the substituents on the ligands. The catalytic behavior of complexes 1 a–6 a in the CO/styrene and CO/p‐Me‐styrene copolymerizations was studied in detail, showing that the generated catalysts are active for at least 90 h, yielding copolymers of high molecular weight. A firm correlation between the electron density on palladium on the one hand and the catalytic activity of the complexes and the molecular weight and the stereochemistry of the polyketones synthesized on the other hand has been established: the catalyst containing the F4‐phen is thus far the most active among those tested, yielding the syndiotactic CO/styrene copolymer with a stereoregularity of 96 % (uu triad) and with an Mw value of 1 000 000.
Significantly Accelerated Direct Electron‐Transfer Kinetics of Hemoglobin in a C60‐MWCNT Nanocomposite Film
Authors: Zhang Hua , Fan Louzhen , Yang Shihe
Published: June 2006

The direct electrochemistry of hemoglobin (Hb) was studied in a novel all‐carbon nanocomposite film of C60‐MWCNT (MWCNT=multiple‐walled carbon nanotube) and compared with that in bare MWCNT film. The heterogeneous electron‐transfer rate constant ks of Hb/C60‐MWCNT was determined to be 0.39 s−1, which is more than one order of magnitude greater than that of Hb/MWCNT (0.03 s−1). The significantly accelerated electron‐transfer kinetics are attributed to the mediator role played by C60, which is finely dispersed on the MWCNT surfaces. The excellent stability of Hb/C60‐MWCNT was established and its potential application towards the electrocatalytic reduction of O2 was demonstrated.
Characterising the Electronic Structure of Ionic Liquids: An Examination of the 1‐Butyl‐3‐Methylimidazolium Chloride Ion Pair
Authors: Hunt Patricia A. , Kirchner Barbara , Welton Tom
Published: June 2006

In this paper we analyse the electronic properties of gas‐phase 1‐butyl‐3‐methylimidazolium Cl ion pairs, [C4C1im]Cl, in order to deepen our understanding of ionic liquids in general. Examination of charge densities, natural bond orbitals (NBO), and delocalised molecular orbitals computed at the B3LYP and MP2/6‐31++G(d,p) levels have enabled us to explain a number of experimental phenomena: the relative acidity of different sites on the imidazolium ring, variations in hydrogen‐bond donor and acceptor abilities, the apparent contradiction of the hydrogen‐bond‐donor parameters for different types of solute, the low probability of finding a Cl− anion at the rear of the imidazolium ring and the expansion of the imidazolium ring in the presence of a strong hydrogen‐bond acceptor. The unreactive but coordinating environment and large electrochemical window have also been accounted for, as has the strong electron‐donating character of the carbon atoms to the rear of the ring in associated imidazolylidenes. The electronic structure of the [C4C1im]+ cation is best described by a C4C5 double bond at the rear, and a delocalised three‐centre 4 e− component across the front (N1‐C2‐N3) of the imidazolium ring; delocalisation between these regions is also significant. Hydrogen‐bond formation is driven by Coulombic stabilisation, which compensates for an associated destabilisation of the electronic part of the system. Interactions are dominated by a large positive charge at C2 and the build up of π‐electron density above and below the ring, particularly that associated with the double bond between C4 and C5. The NBO partial charges have been computed and compared with those used in a number of classical simulations.
Ruthenation of Duplex and Single‐Stranded d(CGGCCG) by Organometallic Anticancer Complexes
Authors: Liu Hong‐Ke , Wang Fuyi , Parkinson John A. , Bella Juraj , Sadler Peter J.
Published: June 2006

We have studied the interaction of the organometallic anticancer ruthenium(II) complexes [(η6‐p‐cymene)Ru(en)Cl][PF6] (1) and [(η6‐biphenyl)Ru(en)Cl][PF6] (2) (en=ethylenediamine) with the single‐stranded (ss) DNA hexamer d(CGGCCG) (I) and the duplex d(CGGCCG)2 (II) by HPLC, ESI‐MS, and one‐ and two‐dimensional 1H and 15N NMR spectroscopy. For ss‐DNA, all three G's are readily ruthenated with [(η6‐arene)Ru(en)]2+, but for duplex DNA there is preferential ruthenation of G3 and G6, and no binding to G2 was detected. For monoruthenated duplexes, N7 ruthenation of G is accompanied by strong hydrogen bonding between G‐O6 and en‐NH for the p‐cymene adducts. Intercalation of the non‐coordinated phenyl ring between G3 and C4 or G6 and C5 was detected in the biphenyl adducts of mono‐ and diruthenated duplexes, together with weakening of the G‐O6⋅⋅⋅NH‐en hydrogen bonding. The arene ligand plays a major role in distorting the duplex either through steric interactions (p‐cymene) or through intercalation (biphenyl).
Carbonic Anhydrase Activators. Activation of Isozymes I, II, IV, VA, VII, and XIV withL‐ andD‐Histidine and Crystallographic Analysis of Their Adducts with Isoform II: Engineering Proton‐Transfer Processes within the Active Site of an Enzyme
Authors: Temperini Claudia , Scozzafava Andrea , Vullo Daniela , Supuran Claudiu T.
Published: June 2006

Activation of six human carbonic anhydrases (CA, EC 4.2.1.1), that is, hCA I, II, IV, VA, VII, and XIV, withl‐andd‐histidine was investigated through kinetics and by X‐ray crystallography.l‐His was a potent activator of isozymes I, VA, VII, and XIV, and a weaker activator of hCA II and IV.d‐His showed good hCA I, VA, and VII activation properties, being a moderate activator of hCA XIV and a weak activator of hCA II and IV. The structures as determined by X‐ray crystallography of the hCA II–l‐His/d‐His adducts showed the activators to be anchored at the entrance of the active site, contributing to extended networks of hydrogen bonds with amino acid residues/water molecules present in the cavity, explaining their different potency and interaction patterns with various isozymes. The residues involved inl‐His recognition were His64, Asn67, Gln92, whereas three water molecules connected the activator to the zinc‐bound hydroxide. Only the imidazole moiety ofl‐His interacted with these amino acids. For thed‐His adduct, the residues involved in recognition of the activator were Trp5, His64, and Pro201, whereas two water molecules connected the zinc‐bound water to the activator. Only the COOH and NH2moieties ofd‐His participated in hydrogen bonds with these residues. This is the first study showing different binding modes of stereoisomeric activators within the hCA II active site, with consequences for overall proton‐transfer processes (rate‐determining for the catalytic cycle). The study also points out differences of activation efficiency between various isozymes with structurally related activators, convenient for designing alternative proton‐transfer pathways, useful both for a better understanding of the catalytic mechanism and for obtaining pharmacologically useful derivatives, for example, for the management of Alzheimer's disease.