bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractSummary: 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.magnified imageMALDI‐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

AbstractPolyurethanes 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

AbstractWe 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

AbstractWe 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

AbstractWe 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

AbstractThe 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

AbstractThe 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

AbstractWe 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

AbstractThe 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

AbstractWe 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

AbstractThe 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

AbstractBethe 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

AbstractThe 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

AbstractWe 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

AbstractOn‐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

AbstractTarget 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

AbstractWe 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.
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

AbstractPhlyctis 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.
TOWARD AN ECONOMIC THEORY OF REALITY: AN INTERVIEW WITH GUILLERMO A. CALVO
Authors: MENDOZA ENRIQUE G. 
Published: January 2005

Guillermo Calvo is one of the most influential economists in the field of international macroeconomics of the past 30 years. He has produced seminal articles in every area of macroeconomics and international economics that he has worked on, including his early classic articles on capacity utilization and time inconsistency, his 1980's works on efficiency wages, price stickiness, and policy credibility, and his recent studies on sudden stops and emerging market crises. Yet, the defining feature of Guillermo Calvo's contribution to our profession is not the depth and wide scope of the economic theories he has developed, but the central emphasis he puts in all his work on the role of economics as a tool for understanding reality and improving the quality of human life.Guillermo Calvo's passion for the policy implications of economic theory is obvious to anyone who has met him since his days as Senior Advisor of the Research Department of the IMF in the mid-1980's. This feature of his professional interests was much less obvious to those who interacted with him during his early years as an important figure of the rational expectations revolution. It was probably hard to see that behind the highly technical treatment presented in his articles at that time was an author who had his feet soundly set on the ground and focused on understanding how society could benefit from the renaissance of macroeconomic theory that was taking place. Interestingly, Michael Rothschild did figure out the true nature of Guillermo Calvo in those early years. When the University of California at San Diego tried to hire Calvo in the mid-1980's, Rothschild explained to Calvo that he was an excellent fit for San Diego because he was a particular type of theoretician: “Most theoreticians make theory out of theory,” Rothschild noted, but Calvo was different because he made “theory out of reality, taking what is really out there and presenting it in a much wider and complex form than a well-developed but narrow theory.”The following pages are excerpts from three interview sessions that Guillermo Calvo and I had at his office in the Inter-American Development Bank in the spring of 2003. These interviews provide a clear summary picture of Calvo as the theoretician of reality that Michael Rothschild described. The recollection of the conversation with Rothschild is one of many fascinating memories of Calvo's personal life and professional career that emerged during our meetings. We taped and transcribed the three meetings in Spanish and then Calvo and I together edited that material to produce this much shorter interview in English for Macroeconomic Dynamics.
Imidapril treatment improves the attenuated inotropic and intracellular calcium responses to ATP in heart failure due to myocardial infarction
Authors: Saini Harjot K , Shao Qiming , Musat Sorin , Takeda Nobuakira , Tappia Paramjit S , Dhalla Naranjan S 
Published: January 2005

M Adenosine 5′‐triphosphate (ATP) is known to augment cardiac contractile activity and cause an increase in intracellular Ca2+ concentration ([Ca2+]i) in isolated cardiomyocytes. However, no information regarding the ATP‐mediated signal transduction in the myocardium in congestive heart failure (CHF) is available.
CHF due to myocardial infarction (MI) in rats was induced by the occlusion of the left coronary artery for 8 weeks. The positive inotropy due to ATP was depressed in failing hearts. Treatment of 3 weeks infarcted animals with imidapril (1 mg kg−1 day−1) for a period of 5 weeks improved the left ventricle function and decreased the attenuation of inotropic response to ATP.
ATP‐induced increase in [Ca2+]i was significantly depressed in cardiomyocytes isolated from the failing heart and this change was partially attenuated by imidapril treatment. However, the binding characteristics of 35S‐labeled adenosine 5′‐(γ‐thio) triphosphate in sarcolemma isolated from the failing heart remained unaltered.
ATP‐induced increase in [Ca2+]i was depressed by verapamil and cibacron blue in both control and failing heart cardiomyocytes; however, the ATP response in the failing hearts, unlike the control preparations, was not decreased by ryanodine. This insensitivity to ryanodine was attenuated by imidapril treatment.
Treatment of infarcted rats with enalapril and losartan produced effects similar to imidapril.
These findings indicate that the positive inotropic response to ATP and ATP‐induced increase in [Ca2+]i in cardiomyocytes are impaired in heart failure. Furthermore, blockade of renin angiotensin system prevented the impairment of the ATP‐mediated inotropic and [Ca2+]i responses in the failing heart.

British Journal of Pharmacology (2005) 144, 202–211. doi:10.1038/sj.bjp.0705867