bluuebunny/crossref_metadata_2025 huggingface dataset:
Dispersion Behavior of TiO2 Nanoparticles in LLDPE/LDPE/TiO2 Nanocomposites
Authors: Wang Zhaobo , Li Guicun , Xie Guangwen , Zhang Zhikun
Published: January 2005

Summary: TiO2 nanoparticles were introduced into linear low‐density polyethylene (LLDPE)/low‐density polyethylene (LDPE) composite films in the form of master batch where TiO2 was pre‐dispersed in LDPE by melt compounding. The dispersion behavior of TiO2 nanoparticles was investigated by field‐emission scanning electron microscopy (FE‐SEM). The rheology results show that the viscosity of LDPE/TiO2 master batch is lower than that of LLDPE/LDPE composites. Energy dispersive X‐ray spectrometer (EDS) composition distribution map indicates that TiO2 nanoparticles were dispersed randomly in the master batch. Scanning electron microscopy (SEM) images show that LDPE/TiO2 master batch is crushed into micron scale dispersed phases due to the shear stress during the blow‐forming process. Subsequently, TiO2 nanoparticles in the dispersed phases are released into the ambient matrix and form a wide ring composed of monodispersed particles. The sizes of spherical crystals decrease due to the presence of TiO2 nanoparticles in LLDPE/LDPE/TiO2 nanocomposites. The transparency of LLDPE/LDPE/TiO2 composite films decreases little compared to that of LLDPE/LDPE composite films.

SEM image of TiO2 nanoparticles dispersed randomly in LLDPE/LDPE/TiO2 composite films.

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SEM image of TiO2 nanoparticles dispersed randomly in LLDPE/LDPE/TiO2 composite films.
Photochemical Surface Modification of Polytetrafluoroethylene with Hydrazine: Characterization of the Surface with Zeta‐Potential Measurements and Spectroscopic Techniques
Authors: Meyer Ursula , Köstler Stefan , Ribitsch Volker , Kern Wolfgang
Published: January 2005

Summary: Surfaces of PTFE were modified by polychromatic UV irradiation in the presence of hydrazine vapors. The surfaces were characterized by FTIR and XP spectroscopy as well as by zeta‐potential and contact angle measurements. FTIR spectroscopy revealed that – in addition to the introduction of amino and hydrazinyl groups onto the PTFE surface – a partial hydrogenation of the CF units proceeds (generation of hydrocarbon units CH). This finding is backed by XPS results. A fraction of the photochemically modified PTFE layers is soluble in aqueous media, while hydrogenated units appear to be more stable. The determination of the zeta potential (ζ) of the PTFE surface showed a shift of the isoelectric point towards higher pH values as a result of the surface modification. The zeta potential vs. pH curves are shifting steadily towards more positive values at increasing duration of the N2H4/UV treatment. The analysis of the surface tension components of hydrazine‐modified PTFE indicates a strong increase of the Lifshitz‐Van der Waals components (γLW) and electron‐donor components (γ−) compared to untreated PTFE. These components change in different fashion after extraction of the PTFE surface with aqueous media. Finally it is shown that amino and hydrazinyl groups at the PTFE surface can be derivatized by polymer‐analogous reactions with isothiocyanates and anhydrides.

Zeta‐potential versus pH plots of modified PTFE samples. Dependence on the UV irradiation time in the presence of hydrazine vapor. (○) 0 min; (▴) 30 min; (▾) 45 min; (♦) 70 min; (▪) 90 min; (•) 120 min.

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Zeta‐potential versus pH plots of modified PTFE samples. Dependence on the UV irradiation time in the presence of hydrazine vapor. (○) 0 min; (▴) 30 min; (▾) 45 min; (♦) 70 min; (▪) 90 min; (•) 120 min.
Effect of the Polyimide Structure and ZnO Concentration on the Morphology and Characteristics of Polyimide/ZnO Nanohybrid Films
Authors: Hsu Shou‐Chian , Whang Wha‐Tzong , Hung Chin‐Hsien , Chiang Pei‐Chun , Hsiao Yi‐Nan
Published: January 2005

Summary: A series of polyimide/ZnO nanohybrid films with different ZnO content were prepared from a rigid pyromellitic dianhydride‐4,4′‐diaminodiphenyl ether (PMDA‐ODA) polyimide (PI) and a flexible 3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride‐4,4′‐diaminodiphenyl ether (BTDA‐ODA) PI with ZnO nanoparticles (3–4 nm). Fourier‐transform infrared (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) depict that the ZnO nanoparticles function as a physical cross‐linking agent with PI through hydrogen bonding between the OH on the ZnO nanoparticles and the CO of the imide groups. ZnO nanoparticles in the rigid PMDA‐ODA matrix cause a larger percentage decrease in the coefficient of linear thermal expansion (CTE) than in the flexible BTDA‐ODA matrix. The BTDA‐ODA/ZnO hybrid films have two transition peaks in dynamic mechanical tan δ curves, but PMDA‐ODA/ZnO hybrid films only have one transition peak. Thermogravimetric analysis reveals that ZnO decreases the thermal degradation temperature (Td) in both hybrid films, but less so in PMDA‐ODA/ZnO films. Transmission electron microscopy (TEM) images reveal that the rigid matrix induces larger particle size (30–40 nm) compared to the flexible matrix (10–15 nm).

Illustration of the interaction between ZnO nanoparticles and PI.

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Illustration of the interaction between ZnO nanoparticles and PI.
Proton Conductivity of Acid Doped Styrene‐Maleic Imide Copolymer With Benzimidazole Side Group
Authors: Pu Hongting , Qiao Lei
Published: January 2005

Summary: Styrene‐maleic imide copolymer with benzimidazole side group was prepared from 2‐amino‐benzimidazole and styrene‐maleic anhydride copolymer. The structures of the new styrene‐maleic imide copolymers from both random and alternating styrene‐maleic anhydride copolymer were characterized by FTIR, DSC, and gel permeation chromatography (GPC). Styrene‐maleic imide copolymer has good solubility, excellent film forming ability, and is easy to prepare, though the solubility of styrene‐maleic imide copolymer decreases a little with increasing maleic imide. The proton conductivity of phosphoric acid doped styrene‐maleic imide copolymer was studied. The temperature dependence of proton conductivity in H3PO4 doped a‐styrene‐maleic imide copolymer can be fitted by a simple Arrhenius equation very well, while H3PO4 doped r‐styrene‐maleic imide copolymer has somewhat deviation from Arrhenius equation. The structure of alternating copolymer is more favorable for proton transport contributed by hopping mechanism. The proton conductivity of phosphoric acid doped styrene‐maleic imide copolymer can be improved by increasing the acid doping level or the imidazole content.

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Photoreactive Functionalization of Poly(ethylene terephthalate) Track‐Etched Pore Surfaces with “Smart” Polymer Systems
Authors: Geismann Christian , Ulbricht Mathias
Published: January 2005

Summary: Poly(ethylene terephthalate) (PET) track‐etched membranes with a pore diameter of ca. 700 nm, optionally surface‐functionalized to create a “carboxyl” or “amino” surface, were used for heterogeneous graft copolymerizations. Grafted poly(acrylic acid) acted as a pH responsive, “smart” polymer. To evaluate the surface‐specific initiation of graft copolymerizations unmodified and primary functionalized membranes were systematically combined with three differently charged benzophenone derivatives as photoinitiators, which were adsorbed on the PET surface prior to the reaction. The functionalized membranes thus obtained were characterized for chemical structure and permeability as a function of pH. The pore structure with a narrow size distribution and the resulting high sensitivity of the membrane permeability to the grafting functionalizations made the track‐etched PET membranes a very useful tool for analyzing structure and function of responsive grafted polymer layers. The primary functionalization of the base polymer with a molecular layer of a multifunctional alkylamine (“amino” surface) enhanced the efficiency of the subsequent graft copolymerization via photoinitiated hydrogen abstraction considerably because a high density of well accessible reactive groups had been introduced. The preadsorption of the photoinitiator on the base polymer surface was significantly improved by ionic interactions between the respective functional groups of the surface and the photoinitiator. Such a photoinitiator preadsorption, especially when combined with a reactive layer from the primary functionalization, enabled a very efficient and surface selective functionalization because a better control of grafting density and a reduction of photoinitiated side reactions along with a more efficient use of the photoinitiator were possible.

Water permeabilities (pH 2 and pH 7) of unmodified and functionalized PET membranes for identification of optimal synthesis and evaluation conditions.

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Water permeabilities (pH 2 and pH 7) of unmodified and functionalized PET membranes for identification of optimal synthesis and evaluation conditions.
Synthesis of Novel Polycations Using the Chemistry of Ionic Liquids
Authors: Marcilla Rebeca , Blazquez J. Alberto , Fernandez Raquel , Grande Hans , Pomposo Jose A. , Mecerreyes David
Published: January 2005

Summary:In this work, we report the synthesis of a great variety of polycations with varying counter‐anions. These new polymers were obtained by a simple anion exchange reaction facilitated by the phase separation of the resulting products. This strategy has been successfully applied to three different polycations, poly(1‐vinyl‐3‐ethylimidazolium bromide) poly(ViEtIm+Br−), poly(1‐ethyl‐4‐vinylpyridinium bromide) poly(ViEtPy+Br−), and poly(methacryloyloxyethyltrimethylammonium chloride) poly(EMTMA+Cl−), with seven counter‐anions such as PF, CF3SO, (CF3SO2)2N−, (CF3CF2SO2)2N−, dodecylbenzenesulfonate, toluene‐4‐sulfonate, and bis(2‐ethylhexyl) hydrogen phosphate. The solubility range of the new polymeric ionic liquids becomes very broad, including apolar organic solvents and ionic liquids, depending on the nature of the counter‐anion. Thermogravimmetric experiments showed that the thermal stability of the PILs also depends on the nature of the counter‐anion improving in the order CF3SO > (CF3CF2SO2)2N− > C12H25C6H4SO > PF > Br− > C16H34PO.

A simple anion exchange procedure similar to the reaction used in ionic liquids chemistry is used to the synthesis of new polymeric ionic liquids (PILs).

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A simple anion exchange procedure similar to the reaction used in ionic liquids chemistry is used to the synthesis of new polymeric ionic liquids (PILs).
Primary Amine and Solvent‐Induced Polymerizations of L‐ or D,L‐Phenylalanine N‐Carboxyanhydride
Authors: Kricheldorf Hans R. , v. Lossow Colin , Schwarz Gert
Published: January 2005

Summary: Benzylamine, hexylamine and aniline‐initiated polymerizations of D,L‐phenylalanine and L‐phenylalanine N‐carboxyanhydride (D,L‐Phe‐NCA and L‐Phe‐NCA) were performed in various solvents. The isolated polypeptides were characterized by MALDI‐TOF mass spectroscopy. Exclusively linear polypeptides having one amide and one amino endgroup were found, when the polymerizations were conducted in a closed reaction vessel with dioxane or sulfolane as reaction media. Traces of water competed with aniline as initiator, when the reaction vessel was closed with a drying tube. In N,N‐dimethylformamide (DMF) formyl endgroups were formed at polymerization temperatures of 60 °C. In DMF and N‐methylpyrrolidone, cyclic oligo‐ and polypeptides were formed by a solvent‐induced polymerization initiated by zwitterions, which may compete with the primary amine‐initiated polymerizations.

MALDI‐TOF mass spectrum of a poly(D,L‐phenylalanine) polymerized in NMP without addition of an initiator.

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MALDI‐TOF mass spectrum of a poly(D,L‐phenylalanine) polymerized in NMP without addition of an initiator.
Hybrid polymer latexes—acrylics‐polyurethane: II. mechanical properties
Authors: Wang C. , Chu F. , Graillat C. , Guyot A. , Gauthier C.
Published: January 2005

Polyurethanes were prepared from reaction of isophorone diisocyanate (IPDI) with polypropylene glycol (PPG), with chain extension with butanediol (BDO). Their end groups are either methoxy, or methacrylic groups. These polyurethanes (PUs) are dissolved in mixtures of acrylic monomers (methylmethacrylate, MMA, and butylacrylate, BA). The solutions are sonicated to produce miniemulsion droplets, using sodium dodecyl sulfate (SDS) as surfactant, the PU being the hydrophobe. These miniemulsions were polymerized, with an oil‐soluble peroxide initiator. Those latexes with methoxy end groups in the PU are fully soluble, while those containing the acrylic end groups are almost fully crosslinked, but can easily form smooth films. The mechanical properties of these films were studied from their stress–strain curves, and compared with those films formed from the uncrosslinked hybrid latexes. Copyright © 2005 John Wiley & Sons, Ltd.
Strongly correlated multilayered nanostructures near the Mott transition
Authors: Freericks J. K.
Published: January 2005

We examine devices constructed out of multilayered sandwiches of semi‐infinite metal–barrier–semi‐infinite metal, with the barrier tuned to lie near the quantum critical point of the Mott metal–insulator transition. By employing dynamical mean field theory, we are able to solve the many‐body problem exactly (within the local approximation) and determine the density of states through the nanostructure and the charge transport perpendicular to the planes. We introduce a generalization of the Thouless energy that describes the crossover from tunneling to incoherent thermally activated transport. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Collective behavior of coupled mesoscopic cylinders
Authors: Dajka J. , Łuczka J. , Szopa M. , Hänggi P.
Published: January 2005

We address the objective of the generation of finite magnetic flux out of unbiased thermal current fluctuations in a collection of identical mesoscopic cylinders which are coupled via mutual inductances. The influence of thermal Nyquist fluctuations are described in terms of a set of Langevin equations or a corresponding Fokker–Planck equation, respectively. In the limit of infinitely many constituents, the steady‐state of the system is determined by an effective, nonlinear Fokker–Planck equation. The system exhibits in this thermodynamic limit a second‐order phase transition: the average flux through each cylinder changes continuously from zero to non‐zero value and the phase diagram depicts a critical line. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Correlation of Tomonaga–Luttinger liquid, superconductivity, and spin entanglement in carbon nanotubes
Authors: Haruyama J. , Takesue I. , Kobayashi N. , Miyadai S. , Nomura M. , Sato D.
Published: January 2005

We report successful observation of proximity‐induced superconductivity in multi‐walled carbon nanotubes (MWNTs) within a diffusive charge transport regime and also show enhancement of spin entanglement in coherent electron pairs of this MWNT as the 1D anisotropy of MWNTs becomes stronger. By reducing length of this MWNT below mean free path, MWNT can exhibit Tomonaga–Luttinger liquid behaviors. We show a possibility that Cooper pairs, injected from a superconductor electrode, are separated into individual spin by this TLL. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory of electric transport through Fe/V/Fe trilayers including the effect of impurities
Authors: Herper H. C. , Szunyogh L. , Entel P.
Published: January 2005

The influence of Al and Si impurity layers on the giant magnetoresistance (GMR) and the magnetic properties of Fe/V/Fe(110) trilayers is investigated. The calculations are performed by employing the spin‐polarized Kubo–Greenwood approach and the screened Korringa–Kohn–Rostoker method for layered systems. All calculations are carried out with a fully‐relativistic version. Therefore, we are able to consider also anisotropic magnetoresistance effects, which are common in Fe/V systems. We find that the AMR always makes a tiny contribution to the resistivity in alike multilayers so that the magnetoresistance is entirely due to the GMR. A reduction of the GMR due to the Al and Si impurities is observed for current in‐plane (CIP) and perpendicular (CPP) geometry. However, in the case of CIP geometry the influence of the impurities decreases with increasing V layer thickness, whereas in the CPP case the difference alternates between 0 and 7%. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of time‐reversal symmetric gauge fields on the groundstate properties of carbon nanotubes and tori
Authors: Sasaki Ken‐ichi , Kawazoe Yoshiyuki
Published: January 2005

The basic properties of conducting electrons in carbon nanotubes are reviewed from a theoretical perspective, and studies performed on persistent currents in toroidal carbon nanotubes and on the local energy gap in deformed nanotubes are reported on. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Correlated sequential tunneling in Tomonaga–Luttinger liquid quantum dots
Authors: Thorwart M. , Egger R. , Grifoni M.
Published: January 2005

We investigate tunneling through a quantum dot formed by two strong impurites in a spinless Tomonaga–Luttinger liquid. Upon employing a Markovian master equation approach, we compute the linear conductance due to sequential tunneling processes. Besides the previously used lowest‐order Golden Rule rates describing uncorrelated sequential tunneling (UST) processes, we systematically include higher‐order correlated sequential tunneling (CST) diagrams within the standard Weisskopf–Wigner approximation. We provide estimates for the parameter regions where CST effects are shown to dominate over UST. Focusing mainly on the temperature dependence of the conductance maximum, we discuss the relation of our results to previous theoretical and experimental results. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aharonov–Bohm effect in carbon nanotubes and tori
Authors: Margańska Magdalena , Szopa Marek , Zipper Elżbieta
Published: January 2005

The carbon tori and nanotubes, either pure or hole‐doped, are examined. In the two achiral (zigzag and armchair) systems the momentum lines are parallel to the edges of the Brillouin zone or the γ = –γ (γ ≈ 3.03 eV is the overlap integral for graphene) contour. The amplitude and shape of the persistent currents in these cases is predicted by an analysis of the geometry of the reciprocal space, and confirmed by a numerical simulation. Special attention is paid to the differences between the currents in straight nanotube and nanotorus topologies, and other possible configurations of chirality and doping at which the persistent currents may be enhanced are hinted at. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of correlated nanoscopic systems from the exact diagonalization combined with an ab initio approach
Authors: Görlich Edward M. , Rycerz Adam , Spalek Jozef
Published: January 2005

We provide a brief overview of the results for correlated nanoscopic systems obtained from the Exact‐Diagonalization Ab Initio (EDABI) method. Explicitly, after a brief summary of the method and its testing for the atomic and crystal‐field states, we summarize the fundamental properties of nanochains modeling a simple‐metal quantum nanowire. All the results are analyzed as a function of interatomic distance and characterize an evolution of electronic states from the Fermi‐liquid‐like state to a localized state via an intermediate Luttinger‐liquid‐like regime. The renormalized electronic (band) structure and the concept of statistical distribution function are shown to be applicable for N = 8 ÷ 16 atoms arranged in chain or ring configurations. The role of boundary conditions involving a ficticious flux representing the Berry phase is also briefly discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bosonization of dimerized Hubbard chains
Authors: Mocanu C. , Dzierzawa M. , Schwab P. , Eckern U.
Published: January 2005

The role of Klein factors is investigated for the bosonized Hamiltonian of the dimerized Hubbard model. Contrary to previous approaches we take into account their number changing property, i.e. we do not replace them by Majorana fermions. We show how to treat Klein factors in the framework of the self‐consistent harmonic approximation, both for finite systems and in the thermodynamic limit. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A combinatoric description of Bethe Ansatz solutions for nanoscopic systems
Authors: Lulek T.
Published: January 2005

Bethe Ansatz provides an exact classification of eigenstates of the Heisenberg Hamiltonian for a finite magnetic ring, consisting of N nodes, each with the spin s = ½ (with some extensions to an arbitrary spin s) in terms of rigged string configurations. The latter are some combinatorial objects which serve as classification labels for solutions of Bethe equations. An astonishing feature is existence of Robinson–Schensted (RS) and Kerov–Kirillov–Reshetikhin (KKR) bijections between sets of (i) all magnetic configurations, (ii) all pairs of standard Young and Weyl tableaux of N boxes and n = 2s + 1 rows, (iii) all rigged string configurations, for given N and s. These bijections allow to point out an exact correspondence between physically admissible solutions of highly nonlinear Bethe Ansatz equations and the initial basis of quantum calculations – magnetic configurations which are just possible distributions of spins over the nodes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lattice multi‐stability in low‐dimensional structures
Authors: Radosz A. , Ostasiewicz K. , Magnuszewski P. , Radosiński Ł. , Kusmartsev F. V. , Samson J. H.
Published: January 2005

The ground state of an electronic system of compounds revealing photo‐induced phase transitions might be regarded as a multiple‐well, on‐site potential. Different types of asymmetric, multi‐stable potentials correspond to compounds of different types: to spin conversion systems and to charge transfer systems. Thermodynamic properties of one‐dimensional lattice systems with an asymmetric on‐site double well and triple well potential are then considered in quantum and classical approaches. Studying a variety of regimes, one finds that the key feature is a level of asymmetry distinguished as a “shift type” and “shape type” in limiting cases. Nearly singular behaviour of heat capacity in “shape type” systems indicates an entropy driven phase transformation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic and superconducting competition within the Hubbard dimer. Exact solution
Authors: Matlak M. , Słomska T. , Grabiec B.
Published: January 2005

We express the Hubbard dimer Hamiltonian $ H_{d} = {\textstyle \sum \nolimits ^{16} _{\alpha = 1} }E_{\alpha}\vert E_{\alpha}\rangle \langle E_{\alpha}\vert $ in the second quantization with theuse of the Hubbard and spin operators. We consider the case of positive and negative U. We decompose the resulting Hamiltonian into several parts collecting all the terms belonging to the same energy level. Such a decomposition visualizes explicitely all intrinsic interactions competing together and deeply hidden in the original form of the dimer Hamiltonian. Among them are competitive ferromagnetic and antiferromagnetic interactions. There are also hopping terms present which describe Cooper pairs hopping between sites 1 and 2 with positive and negative coupling constants (similar as in Kulik–Pedan, Penson–Kolb models). We show that the competition between intrinsic interactions strongly depends on the model parametrs and the averaged occupation number of electrons n ∈ [0, 4] resulting in different regimes of the model (as e.g. t–J model regime, etc.). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of sulfate‐δ18O upon on‐line sulfate‐δ34S analysis, and implications for measurements of δ33S and Δ33S
Authors: Poulson Simon R.
Published: January 2005

On‐line δ34S analysis of sulfate using an elemental analyzer has a number of advantages vs. conventional off‐line techniques, such as ease of operation, rapidity, and the requirement for small amounts of material. Although the analyses are performed by converting sulfate into SO2 gas, the effect of sulfate‐δ18O composition upon the SO2‐δ18O composition and the value of δ66 during elemental analysis, and ultimately the calculated sulfate‐δ34S composition, has rarely been addressed. Three BaSO4 samples were prepared with known identical δ34S compositions, but with a wide range of δ18O compositions. δ18O values were shown to range over 40‰, but conventional on‐line δ34S analyses verified that the sulfate‐δ34S compositions were identical. These results indicate that conventional on‐line analysis of sulfate‐δ34S is unaffected by the value of sulfate‐δ18O, and suggest that sulfide‐δ34S standards can be used to calibrate sulfate‐δ34S analyses (and vice versa). Moreover, these results suggest that it may be possible to use on‐line sulfur isotope analysis of SO2 to measure δ33S and Δ33S in addition to δ34S, as a faster and safer alternative to the SF6 technique currently utilized, and hence promote further study of mass‐independent sulfur isotope fractionation effects. Copyright © 2004 John Wiley & Sons, Ltd.
Use of quadrupole time‐of‐flight mass spectrometry in the elucidation of unknown compounds present in environmental water
Authors: Ibáñez María , Sancho Juan V. , Pozo Óscar J. , Niessen Wilfried , Hernández Félix
Published: January 2005

Target compound monitoring is often not sufficient to assess the quality of water, as many of the unknown micro‐contaminants present might be a threat to the environment and human health. In this work, the potential of hybrid quadrupole time‐of‐flight mass spectrometry (QTOF‐MS) coupled to liquid chromatography (LC) in the elucidation of unknown compounds in environmental water samples has been explored. Based on accurate mass measurement, possible elemental compositions for the precursor ions were calculated. Using model compounds, a useful strategy was developed, enabling determination and evaluation of potential molecular formulae for the detected unknowns. The possibility of performing tandem mass spectrometric (MS/MS) acquisitions to obtain product ion spectra in accurate mass mode also helped to elucidate the structures of these unknowns or to detect some functional groups, to further evaluate potential formulae. The remaining formulae were searched against available databases such as the Merck Index and the NIST library. Where standards were commercially available, retention time and MS/MS data were both also used as confirmatory tools. The approach developed was applied for the identification of unknown compounds in different types of water. To improve sensitivity, environmental water samples were preconcentrated on‐line in a polymeric cartridge by direct injection of 2 mL water into the SPE‐LC/MS/MS system. For three unknowns, structures were proposed and confirmed with standards. Although other compounds could not be unequivocally identified based on the data available within this study, details about the possible structures of some are given. Copyright © 2004 John Wiley & Sons, Ltd.
A sheath‐flow nanospray interface for capillary electrophoresis/mass spectrometry
Authors: Liu Charles C. , Zhang Jianzhong , Dovichi Norman J.
Published: January 2005

We have developed a novel sheath‐flow interface for low‐flow electrospray ionization mass spectrometry (ESI‐MS) and capillary electrophoresis/electrospray mass spectrometry (CE/ESI‐MS). The interface is composed of two capillaries. One is a tapered fused‐silica ESI emitter suitable for microliter and nanoliter flow rate electrospray and the other is a tail‐end gold‐coated CE separation column that is inserted into the emitter. A sheath liquid is supplied between the column and the emitter capillaries. The gold coating and the sheath liquid are used as the conducting media for ESI and the CE circuit. This novel design was initially evaluated by an infusion ESI‐MS analysis of the most common antiretroviral dideoxynucleosides, followed by CE/MS coupling analysis of several antidepressant drugs. With infusion studies, the effects of the sheath liquid and the sample flow rates on detection sensitivity and signal stability were investigated. For an emitter with an internal diameter of 30 μm, the optimum flow rates for the sheath and the sample were 200 and 300 nL/min, respectively. The main improvement of this approach in comparison with conventional sheath liquid approaches using an ionspray interface is the gain in sensitivity. Sensitivities were three times better for dideoxynucleosides analyzed by infusion and 12 times higher for antidepressant drugs analyzed by CE/MS with this interface compared with ionspray. The emitter is durable, disposable, and simple to fabricate. Copyright © 2004 John Wiley & Sons, Ltd.
Ubiquitination of RhoA by Smurf1 promotes neurite outgrowth
Authors: Bryan Brad , Cai Yi , Wrighton Katharine , Wu Gangyi , Feng Xin-Hua , Liu Mingyao
Published: January 2005

The Rho‐family of small GTPases consists of essential regulators of neurite outgrowth, axonal pathfinding, and dendritic arborization. Previous work has demonstrated in non‐neuronal cell types that Smurf1, an E3 ubiquitin ligase, regulates cell polarity and protrusive activity via PKCζ‐dependent recruitment to cellular protrusion sites, and subsequent ubiquitination and proteasomal degradation of RhoA. In this study, we show that Smurf1 enhances neurite outgrowth in Neuro2a neuroblastoma cells. We demonstrate that RhoA is ubiquitinated, and that Smurf1 and RhoA physically interact in vivo. Interestingly, Smurf1 overexpression in Neuro2a cells dramatically reduces RhoA protein levels during dibutyric cyclic AMP, but not retinoic acid induced neurite outgrowth. This Smurf1‐dependent reduction in RhoA protein levels was abrogated using the general proteasome inhibitor MG132, suggesting that RhoA is targeted for ubiquitination and degradation via Smurf1. Together, our data suggest that localized regulation of different subsets of Rho GTPases by specific guidance signals results in an intracellular asymmetry of RhoA activity, which could regulate neurite outgrowth and guidance.
Dictyochloropsis Splendida (Chlorophyta), the Correct Phycobiont of Phlyctis Argena and the High Degree of Selectivity or Specificity Involved
Authors: Tschermak–Woess Elisabeth
Published: January 2005

Phlyctis argena is lichenized with Dictyochloropsis splendida and not with D. reticulata, as thought formerly. This results from in-situ investigation of over 150 lichen thalli and more than 70 cultures of the phycobiont. Material studied from a wide range of geographical locations indicates that specificity of the association in this case is highly probable. Compared to the free–living state, the alga as a lichen partner undergoes distinct changes. Differentiation of strains of D. splendida with respect to morphology and development was not observed.
GROUNDNUT, MAIZE AND CASSAVA YIELDS IN MIXED-FOOD CROP FIELDS AFTER CALLIANDRA TREE FALLOW IN SOUTHERN CAMEROON
Authors: NOLTE C. , TIKI-MANGA T. , BADJEL-BADJEL S. , GOCKOWSKI J. , HAUSER S.
Published: January 2005

Shortened fallow periods lead to a decline in crop yields in traditional mixed-food crop fields in southern Cameroon. Farmers use no inputs such as fertilizers for crop production in these field types. Planted fallows with adapted tree species might sustain or increase crop production under those conditions, as found in other parts of Africa. Two-year-old calliandra tree fallows, with trees planted in alleys, clusters, equidistantly or around plot borders, were compared with two- and four to five-year-old natural fallows for their effect on groundnut, maize and cassava yields on eighteen farmer fields in southern Cameroon. Trial fields covered a wide range of soil and environmental conditions. The tree fallows had no significant effects on the yields of maize and cassava with the exception of the border planting, in which trees were not rigorously pruned back prior to cropping. Here, cassava tuber yields were reduced. Cassava tuber yields declined generally with decreasing planting distance to trees. The yield of groundnut, the most important crop in this field type, was adversely affected. However, maize grain yields were positively related to biomass produced by calliandra trees, notably on soils with pH over about 5.3. The data indicated that yields of all crops could be increased with higher plant densities, irrespective of fallow type. The tree fallows, with the exception of border planting, showed less adaptability than four to five-year-old natural fallows to sites with low crop yields, whereas no difference compared with two-year-old natural fallows was found.
CROP PRODUCTIVITY AND SOIL FERTILITY IN A TROPICAL DRYLAND AGRO-ECOSYSTEM: IMPACT OF RESIDUE AND TILLAGE MANAGEMENT
Authors: KUSHWAHA C. P. , SINGH K. P.
Published: January 2005

To understand the impact of residue and tillage management on crop productivity of rice and barley (including grain yield) and soil fertility in a tropical dryland agro-ecosystem, the following six treatments were established: (a) conventional tillage and residue removed (CT−R); (b) conventional tillage and residue retained (CT+R); (c) minimum tillage and residue removed (MT−R); (d) minimum tillage and residue retained (MT+R); (e) zero tillage and residue removed (ZT−R); and (f) zero tillage and residue retained (ZT+R). Minimum total net productivity (TNP) in both barley (the winter season crop) and rice (the rainy season crop) was recorded in the ZT−R treatment and the maximum in the MT+R treatment. In these crops, 83–88% of TNP was represented by above-ground net productivity (ANP). A reduction in tillage, from conventional to zero, especially when combined with residue retention, reduced the crop TNP/weed TNP ratio, reflecting the abundance of weeds with zero tillage. In both crops, minimum tillage increased grain yields, compared with conventional, but zero tillage resulted in reduced yields. Soil microbial biomass carbon (MBC) and nitrogen (MBN) and N-mineralization rates were higher in rice than in barley, and were maximum in the MT+R treatment. Crop productivity and grain yield in different treatments were positively correlated with MBC, MBN, N-mineralization rate and available-N. Strong negative correlations between crop productivity and grain yield with weed TNP and N-uptake were recorded. This study suggests that retention of a small fraction (one-third) of above-ground biomass from the previous crop and its incorporation in the soil through minimum tillage enhances the crop productivity and grain yield of succeeding crops and promotes soil fertility in a cereal based tropical dryland agro-ecosystem.
EFFECTS OF FALLOW DURATION ON SOIL PHOSPHORUS FRACTIONS AND CROP P UPTAKE UNDER NATURAL REGROWTH AND PLANTED PUERARIA PHASEOLOIDES FALLOW SYSTEMS IN SOUTHWESTERN NIGERIA
Authors: KOLAWOLE G. O. , TIAN G. , TIJANI-ENIOLA H.
Published: January 2005

Soil phosphorus fractions, maize and cassava P uptakes in natural regrowth fallow and Pueraria phaseoloides fallow systems, as affected by the duration (1–3 years) of fallow, were assessed in 1998 and 1999 in a long-term fallow management trial, established in 1989 at the International Institute of Tropical Agriculture, Ibadan, Nigeria. After one and three years fallow respectively, the mean P accumulation in fallow vegetation was 4.2 and 9.4 kg ha−1 in 1998, and 8.9 and 12.1 kg ha−1 in 1999 for natural fallow. For Pueraria, the corresponding values were 6.3 and 7.4 kg ha−1 in 1998 and 6.1 and 13.5 kg ha−1 in 1999. The positive effects of fallow lengths on dry matter and P accumulation were not as pronounced under Pueraria. Continuous cropping reduced soil pH and depleted Olsen P more than crop-fallow rotations under both fallow systems. An increase in fallow duration enhanced the availability of resin P, NaHCO3-, and NaOH- extractable P fractions, especially under natural fallow. Continuous cropping in a natural fallow system resulted in lower resin inorganic P (Pi) and NaHCO3-extractable inorganic and organic P (Po) fractions, and higher refractory P fractions (concentrated HCl-extractable Pi and Po and residual P) as compared to crop-fallow rotations. Although continuous cropping in the Pueraria system resulted in higher refractory P fractions than the crop-fallow rotations, the effects of fallow length on P fractions were not consistent or pronounced. Maize and cassava P uptakes increased with fallow duration. Phosphorous in maize grain was positively correlated with fallow vegetation P accumulation. Total P uptake by maize was positively but weakly correlated with NaHCO3-Po, Olsen P and fallow vegetation P accumulation.
PARTICIPATORY EVALUATION OF TEPHROSIA SPECIES AND PROVENANCES FOR SOIL FERTILITY IMPROVEMENT AND OTHER USES USING FARMER CRITERIA IN EASTERN ZAMBIA
Authors: MAFONGOYA PARAMU L. , KUNTASHULA ELIAS
Published: January 2005

In eastern Zambia, farmers prefer direct seeded improved fallow species like Tephrosia vogelii to other species because of the reduced labour requirement for establishment. Since relying on two locally available provenances of T. vogelii could become ecologically unsustainable, due to pest and disease outbreaks, a wider range of usable direct seeded Tephrosia provenance material is desirable. A farmer participatory evaluation of Tephrosia candida provenances for their effectiveness as improved fallows and provision of construction materials and fuel wood was conducted. Using an indigenous board game called bao, 68 farmers rated the four provenances and five control species/provenances for these benefits. The T. candida provenances were rated high for soil fertility improvement. First year T. candida post-fallow performance showed that maize yields could be obtained that were comparable with yields following Tephrosia vogelii provenances. According to farmers' ratings, T. candida provenances could provide better fuel wood and light construction materials than T. vogelii, although they were not considered to be as good as Sesbania sesban and Senna siamea. Tephrosia candida provenances have the potential to be tested by many farmers on-farm. Farmers' methods of screening trees can complement scientific predictors, and their early integration into the selection and design of agro-forestry systems can improve relevance and adoption.
EFFECTS OF WATER AVAILABILITY AND VINE HARVESTING FREQUENCY ON THE PRODUCTIVITY OF SWEET POTATO IN SOUTHERN MOZAMBIQUE. IV. RADIATION INTERCEPTION, DRY MATTER PRODUCTION AND PARTITIONING
Authors: GOMES F. , CARR M. K. V. , SQUIRE G. R.
Published: January 2005

In Mozambique, the sweet potato (Ipomoea batatas) is grown both as a leafy vegetable, the terminal shoots or vines being progressively harvested during the season, and as a root crop. It is produced in the dry season, in areas with a high water table or with irrigation, and in the rainy season. This paper reports the results of measurements made during the 1995 dry season to evaluate the effects of water availability and the frequency of vine harvesting on the processes of radiation interception, dry matter production and partitioning. An irrigated crop (cv. TIS 2534) with a single, end of season vine-harvest (H1) intercepted 71% of the total solar radiation, reducing to 52% with weekly (H4) harvests. The corresponding values for a rain-fed crop were 33 and 20% respectively. When the leaf area index (L) exceeded 3–4, virtually full interception of photosynthetically active radiation (PAR) occurred, except when frequent vine-harvests modified the architecture of the leaf canopy. The extinction coefficient (k, PAR) was highly variable: at a given leaf area, interception was greatest earlier in the season, with infrequent harvests and with irrigation. Total dry matter production (vines, foliage and storage roots), over a period of 161 days, reached 23 t ha−1 in the single harvest (H1), irrigated crop, less when the vines were harvested weekly (H4). The corresponding value for the rain-fed crop, which was able to resume active growth immediately after a rainfall event, following a prolonged dry period, was 7 t ha−1. The efficiency of conversion of PAR into dry matter (εs) was 2.74 g MJ−1 in the irrigated treatments combined, decreasing to around 73% of this without irrigation. The value of εs appeared not to be influenced by dry air or high temperatures. The reduction in εs due to drought was less than the corresponding reduction in intercepted PAR. Increasing the frequency of vine harvests increased the partitioning of assimilates to vines. Irrigation had similar effects early in the season, but afterwards it encouraged preferential growth of the storage roots. The end of season harvest index (h) for vines increased with harvesting frequency from, for example, 0.08 (H1) to 0.38 (H4) in the irrigated crop. By comparison, irrigation increased ‘h’ for storage roots from 0.24 (rain-fed) to 0.57 in the H1 treatment. The total harvest index (vines plus roots) increased with the number of vine harvests from 0.32 (H1) to 0.55 (H4) in the rain-fed crop, and from 0.62 (H1) to 0.72 (H4) in the irrigated crop. Clearly, ‘h’ is not a conservative parameter in the sweet potato, but is sensitive to crop management practices and to soil water availability.
THE FACTORIAL FIELD EXPERIMENT
Authors: PEARCE S. C.
Published: January 2005

Factorial experiments are described and the importance of interactions emphasized with suggestions about how they should be interpreted. A distinction is made between factors introduced only to see if they will provoke an interaction and those actually under study. Split-plot designs receive special attention. Factorial experiments often involve a large number of treatments and ordinary block designs may be ineffective in controlling environmental variation. If factors have few levels, as in exploratory experiments, the usual device for reducing block size is confounding, which is explained along with single-replicate experiments, partial replication and hidden replication. Alternatively, non-orthogonal designs and analysis of data by nearest-neighbour and spatial methods might prove useful. The need for randomization and the role of significance are discussed. It is pointed out that interactions can sometimes be avoided by transformation of the variate.
Towards a balanced social psychology: Causes, consequences, and cures for the problem-seeking approach to social behavior and cognition
Authors: Krueger Joachim I. , Funder David C.
Published: January 2005

Mainstream social psychology focuses on how people characteristically violate norms of action through social misbehaviors such as conformity with false majority judgments, destructive obedience, and failures to help those in need. Likewise, they are seen to violate norms of reasoning through cognitive errors such as misuse of social information, self-enhancement, and an over-readiness to attribute dispositional characteristics. The causes of this negative research emphasis include the apparent informativeness of norm violation, the status of good behavior and judgment as unconfirmable null hypotheses, and the allure of counter-intuitive findings. The shortcomings of this orientation include frequently erroneous imputations of error, findings of mutually contradictory errors, incoherent interpretations of error, an inability to explain the sources of behavioral or cognitive achievement, and the inhibition of generalized theory. Possible remedies include increased attention to the complete range of behavior and judgmental accomplishment, analytic reforms emphasizing effect sizes and Bayesian inference, and a theoretical paradigm able to account for both the sources of accomplishment and of error. A more balanced social psychology would yield not only a more positive view of human nature, but also an improved understanding of the bases of good behavior and accurate judgment, coherent explanations of occasional lapses, and theoretically grounded suggestions for improvement.
The emulation theory of representation: Motor control, imagery, and perception
Authors: Grush Rick
Published: January 2005

The emulation theory of representation is developed and explored as a framework that can revealingly synthesize a wide variety of representational functions of the brain. The framework is based on constructs from control theory (forward models) and signal processing (Kalman filters). The idea is that in addition to simply engaging with the body and environment, the brain constructs neural circuits that act as models of the body and environment. During overt sensorimotor engagement, these models are driven by efference copies in parallel with the body and environment, in order to provide expectations of the sensory feedback, and to enhance and process sensory information. These models can also be run off-line in order to produce imagery, estimate outcomes of different actions, and evaluate and develop motor plans. The framework is initially developed within the context of motor control, where it has been shown that inner models running in parallel with the body can reduce the effects of feedback delay problems. The same mechanisms can account for motor imagery as the off-line driving of the emulator via efference copies. The framework is extended to account for visual imagery as the off-line driving of an emulator of the motor-visual loop. I also show how such systems can provide for amodal spatial imagery. Perception, including visual perception, results from such models being used to form expectations of, and to interpret, sensory input. I close by briefly outlining other cognitive functions that might also be synthesized within this framework, including reasoning, theory of mind phenomena, and language.
Redundancy in the nervous system: Where internal models collapse
Authors: Balasubramaniam Ramesh
Published: January 2005

Grush has proposed a fairly comprehensive version of the idea of internal models within the framework of the emulation theory of representation. However, the formulation suffers from assumptions that render such models biologically infeasible. Here I present some problems from physiological principles of human movement production to illustrate why. Some alternative views to emulation are presented.
Issues of implementation matter for representation
Authors: Garzón Francisco Calvo
Published: January 2005

I argue that a dynamical framing of the emulation theory of representation may be at odds with its articulation in Grush's information-processing terms. An architectural constraint implicit in the emulation theory may have consequences not envisaged in the target article. In my view, “how the emulator manages to implement the forward mapping” is pivotal with regard to whether we have an emulation theory of representation, as opposed to an emulation theory of (mere) applied forces.
Additional requirements for a balanced social psychology
Authors: Chow Siu L.
Published: January 2005

Ambiguous data obtained by deception say nothing about social behavior. A balanced social psychology requires separating statistical hypotheses from substantive hypotheses. Neither statistical norms nor moral rules are psychological theories. Explanatory substantive theories stipulate the structures and processes underlying behavior. The Bayesian approach is incompatible with the requirement that all to-be-tested theories be given the benefit of the doubt.
Testable corollaries, a conceptual error, and neural correlates of Grush's synthesis
Authors: Campbell Thomas G. , Pettigrew John D.
Published: January 2005

As fundamental researchers in the neuroethology of efference copy, we were stimulated by Grush's bold and original synthesis. In the following critique, we draw attention to ways in which it might be tested in the future, we point out an avoidable conceptual error concerning emulation that Grush seems to share with other workers in the field, and we raise questions about the neural correlates of Grush's schemata that might be probed by neurophysiologists.