bluuebunny/crossref_metadata_2025_split huggingface dataset:
FERROMAGNETIC MONOLAYERS
Authors: ELMERS HANS-JOACHIM 
Published: November 2004

The ferromagnetic properties of ultrathin films grown on non-magnetic substrates provide interesting new insights into the physics of magnetism. In this report we review experiments in the very low coverage regime (Θ < 2 atomic layers). The Fe monolayer on W plays an outstanding role, because it forms a ferromagnetic and thermodynamically stable monolayer. Ferromagnetic Fe monolayers on W can be prepared with a high degree of perfection. We therefore focus on ultrathin Fe films on W(110) and W(100) substrates. Experimental results for these in-plane magnetized films, prepared as close as possible to 2-dimensional structures of perfect translational symmetry, are compared with appropriate theoretical models, We also discuss experimental results for the perpendicularly magnetized Co monolayer on Cu(111). The symmetry of the magnetic anisotropy is found to play an important role for the understanding of the magnetic phase transition in 2 dimensions. A new aspect is provided by finite size effects resulting from the morphology of magnetic ultrathin films. Microscopy with atomic resolution allows a systematic approach to the understanding of these finite size effects. Starting from the well-known magnetic properties of the extended Fe monolayer on W(110), we focus on ultrathin Fe films on W(110) deviating from the nearly perfect structure.
RANK PROBLEMS FOR COMPOSITE TRANSFORMATIONS
Authors: GORALČÍK PAVEL , KOUBEK VÁCLAV 
Published: November 2004

Let (X, F) be a pair consisting of a finite set X and a set F of transformations of X, and, let <F> and F(l) denote, respectively, the semigroup generated by F and the part of <F> consisting of the transformations determined by a generator sequence of length no more than a given integer l. We show the following: • The problem whether or not, for a given pair (X, F) and a given integer r, there is an idempotent transformation of rank r in <F> is PSPACE-complete. • For each fixed r≥1, it is decidable in a polynomial time, for a given pair (X, F), whether or not <F> contains an idempotent transformation of rank r, and, if yes then a generator sequence of polynomial length composing to an idempotent transformation of rank r can be obtained in a polynomial time. • For each fixed r≥1, the problem whether or not, for a given (X, F) and l, there is an idempotent transformation of rank r in F(l) is NP-complete. • For each fixed r≥2, to decide, for a given (X, F), whether or not <F> contains a transformation of rank r is NP-hard.
CONSTRUCTING PARTIAL AND COMPLETE INTELLIGENT ANSWERS FOR RECURSIVE QUERIES
Authors: ZHANG XUBO , OZSOYOGLU Z. MERAL 
Published: November 2004

In this paper we study the issue of providing intelligent answers to recursive queries initially proposed in [Imie88]. In contrast to conventional query answers, which are sets of tuples, intelligent answers are rules describing the characteristics of the results. This way, an intelligent answer facilitates users to better capture the meaning of the query. To this aim, we first extend the notion of intelligent answers by allowing them to be partial (or incomplete). Complete and partial intelligent answers are both useful, in that they provide (possibly partial) characterizations of queries. We will show that complete intelligent answers also give a more efficient way to evaluate queries. For constructing intelligent answers, we propose a general approach that enables us to combine several cases studied in [Imie88]. Moreover, we will show that semantic constraints can be systematically utilized to provide complete intelligent answers to a wider range of queries. We consider two commonly used classes of semantic constraints called implication and referential constraints, and prove that the completeness of intelligent answers with respect to semantic constraints can be reduced to the semantics-based query containment problem. Finally, a necessary and sufficient condition is given to solve this containment problem.
ON THE ARITHMETIC 2-BRIDGE KNOTS AND LINK ORBIFOLDS AND A NEW KNOT INVARIANT
Authors: HILDEN HUGH M. , LOZANO MARIA TERESA , MONTESINOS-AMILIBIA JOSE MARIA 
Published: November 2004

Let (p/q, n) denote the orbifold with singular set the two bridge knot or link p/q and isotropy group cyclic of orden n. An algebraic curve [Formula: see text] (set of zeroes of a polynomial r(x, z)) is associated to p/q parametrizing the representations of [Formula: see text] in PSL [Formula: see text]. The coordinates x, z, are trace(A2)=x, trace(AB)=z where A and B[Formula: see text] are the images of canonical generators a, b of [Formula: see text]. Let (xn, zn) be the point of [Formula: see text] corresponding to the hyperbolic orbifold (p/q, n). We prove the following result: The (orbifold) fundamental group of (p/q, n) is arithmetic if and only if the field Q(xn, zn) has exactly one complex place and ϕ(xn)<ϕ(zn)<2 for every real embedding [Formula: see text]. Consider the angle α for which the cone-manifold (p/q, α) is euclidean. We prove that 2cosα is an algebraic number. Its minimal polynomial (called the h-polynomial) is then a knot invariant. We indicate how to generalize this h-polynomial invariant for any hyperbolic knot. Finally, we compute h-polynomials and arithmeticity of (p/q, n) with p≦40, and (p/q, n) with p≦99q2≡1 mod p. We finish the paper with some open problems.
The Corfu δβ thalassemia deletion disrupts γ-globin gene silencing and reveals post-transcriptional regulation of HbF expression
Authors: Chakalova Lyubomira , Osborne Cameron S. , Dai Yan-Feng , Goyenechea Beatriz , Metaxotou-Mavromati Anna , Kattamis Antonios , Kattamis Christos , Fraser Peter 
Published: November 2004

Abstract
The 7.2 kilobase (kb) Corfu δβ thalassemia mutation is the smallest known deletion encompassing a region upstream of the human δ gene that has been suggested to account for the vastly different phenotypes in hereditary persistence of fetal hemoglobin (HPFH) versus β thalassemia. Fetal hemoglobin (HbF) expression in Corfu heterozygotes and homozygotes is paradoxically dissimilar, suggesting conflicting theories as to the function of the region on globin gene regulation. Here, we measure γ- and β-globin gene transcription, steady-state mRNA, and hemoglobin expression levels in primary erythroid cells cultured from several patients with Corfu δβ thalassemia. We show through RNA fluorescence in situ hybridization that the Corfu deletion results in high-level transcription of the fetal γ genes in cis with a concomitant reduction in transcription of the downstream β gene. Surprisingly, we find that elevated γ gene transcription does not always result in a corresponding accumulation of γ mRNA or fetal hemoglobin, indicating a post-transcriptional regulation of γ gene expression. The data suggest that efficient γ mRNA accumulation and HbF expression are blocked until β mRNA levels fall below a critical threshold. These results explain the Corfu paradox and show that the deleted region harbors a critical element that functions in the developmentally regulated transcription of the β-globin genes.
Genotypic inhibitory killer immunoglobulin-like receptor ligand incompatibility enhances the long-term antileukemic effect of unmodified allogeneic hematopoietic stem cell transplantation in patients with myeloid leukemias
Authors: Beelen Dietrich W. , Ottinger Hellmut D. , Ferencik Stanislav , Elmaagacli Ahmet H. , Peceny Rudolf , Trenschel Rudolf , Grosse-Wilde Hans 
Published: November 2004

AbstractIt remains controversial whether alloreactive donor-derived natural killer (NK) cells display graft-versus-leukemia reactions after unmodified allogeneic hematopoietic stem cell transplantation (HSCT). The present study evaluated the role of inhibitory killer immunoglobulin–like receptor (KIR) ligand incompatibility using a well-defined and uniform setting of unmodified allogeneic HSCT in 374 patients with myeloid leukemias. The most striking finding was a significant heterogeneity in the 5-year estimates of hematologic leukemic relapse after human leukocyte antigen (HLA)–identical (n = 237; 22%), HLA class I–disparate (n = 89; 18%), and KIR ligand–incompatible transplantations (n = 48; 5%) (P &lt; .04). Multivariate analysis confirmed that the relative relapse risk (RR) was influenced by HLA class I disparity alone (RR 0.49), but was lowest after HLA class I–disparate, KIR ligand–incompatible transplantations (RR 0.24) (P &lt; .008). The primary graft failure rates, however, increased from 0.4% after HLA class I–identical to 2.3% after HLA class I–disparate, and to 6.3% after KIR ligand–incompatible transplantations, respectively (P &lt; .02). Unlike some other reports, no beneficial effect of KIR ligand incompatibility on other major endpoints of allogeneic HSCT (transplantation-related mortality, and overall and event-free survival) was detectable in the present study. In conclusion, unmodified allogeneic HSCT from KIR ligand–incompatible donors provides a superior long-term antileukemic efficacy in patients with myeloid malignancies.
Selective inhibition of c-Myb DNA-binding by RNA polymers
Authors: Nordgård Oddmund , Andersen Tor Ø , Gabrielsen Odd S 
Published: November 2004

Abstract
Background
The transcription factor c-Myb is expressed in hematopoietic progenitor cells and other rapidly proliferating tissues, regulating genes important for proliferation, differentiation and survival. The DNA-binding domain (DBD) of c-Myb contains three tandemly arranged imperfect repeats, designated Myb domain R1, R2 and R3. The three-dimensional structure of the DBD shows that only the second and third Myb domains are directly involved in sequence-specific DNA-binding, while the R1 repeat does not contact DNA and only marginally affects DNA-binding properties. No structural information is available on the N-terminal 30 residues. Since deletion of the N-terminal region including R1 plays an important role in oncogenic activation of c-Myb, we asked whether this region confers properties beyond DNA-binding to the neighbouring c-Myb DBD.

Results
Analysis of a putative RNA-binding function of c-Myb DBD revealed that poly(G) preferentially inhibited c-Myb DNA-binding. A strong sequence-selectivity was observed when different RNA polymers were compared. Most interesting, the poly(G) sensitivity was significantly larger for a protein containing the N-terminus and the R1-repeat than for the minimal DNA-binding domain.

Conclusion
Preferential inhibition of c-Myb DNA binding by poly(G) RNA suggests that c-Myb is able to interact with RNA in a sequence-selective manner. While R2 and R3, but not R1, are necessary for DNA-binding, R1 seems to have a distinct role in enhancing the RNA-sensitivity of c-Myb.
Computation of elementary modes: a unifying framework and the new binary approach
Authors: Gagneur Julien , Klamt Steffen 
Published: November 2004

Abstract
Background
Metabolic pathway analysis has been recognized as a central approach to the structural analysis of metabolic networks. The concept of elementary (flux) modes provides a rigorous formalism to describe and assess pathways and has proven to be valuable for many applications. However, computing elementary modes is a hard computational task. In recent years we assisted in a multiplication of algorithms dedicated to it. We require a summarizing point of view and a continued improvement of the current methods.

Results
We show that computing the set of elementary modes is equivalent to computing the set of extreme rays of a convex cone. This standard mathematical representation provides a unified framework that encompasses the most prominent algorithmic methods that compute elementary modes and allows a clear comparison between them. Taking lessons from this benchmark, we here introduce a new method, the binary approach, which computes the elementary modes as binary patterns of participating reactions from which the respective stoichiometric coefficients can be computed in a post-processing step. We implemented the binary approach in FluxAnalyzer 5.1, a software that is free for academics. The binary approach decreases the memory demand up to 96% without loss of speed giving the most efficient method available for computing elementary modes to date.

Conclusions
The equivalence between elementary modes and extreme ray computations offers opportunities for employing tools from polyhedral computation for metabolic pathway analysis. The new binary approach introduced herein was derived from this general theoretical framework and facilitates the computation of elementary modes in considerably larger networks.
Using free bed surface fluctuations in a 3‐D fluidized bed for dynamic characterization
Authors: Villa Briongos Javier , Guardiola Soler Jesús 
Published: November 2004

AbstractThe use of free surface fluctuations in three‐dimensional (3‐D) fluidized bed dynamic characterization is addressed. This technique provides a noninvasive global measure of the quality of fluidization by measuring at one position in the bed. The well‐known effect of particle size on fluidized bed hydrodynamics was explored using a 3D fluidized bed operated with four different particle groups. The analytical methods used were mutual information functions, frequency, and state space analysis of time series collected from bed surface fluctuations. Turbulent, multiple, and noninteracting bubble flow patterns, occurring during bubble regimes, have been characterized. Kolmogorov entropy for the reconstructed attractor is very sensitive to the transition between fluidization regimes. Moreover, correlation dimension estimates ranging between 3 < D2 < 5 indicate apparent low‐dimensional dynamics. Additionally for larger particle groups, D2 reaches a value close to 3, indicating slow bubbling controlled by large bubbles before the transition between different bubble flow patterns takes place. Finally, particle size has been found to have strong influence on signal persistence. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3060–3067, 2004
Reachability of particle size distribution in semibatch emulsion polymerization
Authors: Wang Yang , Doyle Francis J. 
Published: November 2004

AbstractReachability analysis is critical in the determination of achievable end‐point products for complex process systems. In emulsion polymerization, an economically important method of producing various products, particle size distribution (PSD) is an important property of the latex produced. However, the population balance modeling framework does not yield direct solutions to reachability analysis for the resulting nonlinear distributed systems. In this article, a programming‐based approach is introduced for the reachability analysis of the final PSD for general particulate systems described by population balance models. In the application to a semibatch styrene homopolymerization system, the reachable region is defined for both the nominal and perturbed cases, with final PSDs characterized as multi‐Gaussian distributions. Sensitivity studies reveal the limiting factors in determining the achievable final products, and quantitative criteria are developed. The evolution of the reachable region in the case of midcourse correction reveals the difficulties encountered during in‐batch control, and shows the best control performance achievable given the limited on‐line measurements. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3049–3059, 2004
Nonlinear acoustics in pant hoots of common chimpanzees (Pan troglodytes): Frequency jumps, subharmonics, biphonation, and deterministic chaos
Authors: Riede Tobias , Owren Michael J. , Arcadi Adam Clark 
Published: November 2004

AbstractThe pant hoot calls produced by common chimpanzees (Pan troglodytes) are multi‐call vocalizations that have figured prominently in investigations of acoustic communication in this species. Although pant hoots are predominantly harmonically structured, they can exhibit an acoustic complexity that has recently been linked to nonlinearity in the vocal‐fold dynamics underlying typical mammalian sound production. We examined the occurrence of these sorts of nonlinear phenomena in pant hoot vocalizations, contrasting quieter and lower‐pitched “introduction” components with loud and high‐pitched “climax” calls in the same bouts. Spectrographic evidence revealed four kinds of nonlinear phenomena, including discrete frequency jumps, subharmonics, biphonation, and deterministic chaos. While these events were virtually never observed during the introduction, they occurred in more than half of the climax calls. Biphonation was by far the most common phenomenon, followed by subharmonics, chaos, and frequency jumps. Individual callers varied in the degree to which their climax calls exhibited nonlinear phenomena, but were consistent in showing more biphonation than other forms. These outcomes show that nonlinear phenomena are routinely present in chimpanzee pant hoots, and help lay the foundation for investigating the function of such events. Am. J. Primatol. 64:277–291, 2004. © 2004 Wiley‐Liss, Inc.
Characterizing gastrointestinal transit time in four lemur species using barium‐impregnated polyethylene spheres (BIPS)
Authors: Campbell J.L. , Williams C.V. , Eisemann J.H. 
Published: November 2004

AbstractDifferences in dietary profiles and gastrointestinal (GI) morphologies observed across lemur species suggest that there may be variation in patterns of digesta flow through the GI tract related to the method of digesta processing. Using radio‐opaque barium‐impregnated polyethylene spheres (BIPS), we characterized such patterns in four lemur species:Varecia variegata(VV),Eulemur fulvus(EF),Propithecus verreauxi(PV), andHapalemur griseus(HG) (n=2 per species). After an initial radiograph was taken under light sedation, the animals were fed the BIPS together with a small meal. A combination of 30 small (1.5 mm) and 10 large (5 mm) BIPS was administered. Radiographs were then taken on a species‐dependent basis up to 48 hr post‐dosage. For small BIPS, the gastric transit time (GTT; time of first exit of BIPS from stomach) was 0.25–2 hr for VV, EF, and HG, and approximately 10 hr for PV. The oro‐rectal transit time (ORTT; time of first appearance in the rectum) was <2 hr for VV and EF, and 24.0 hr for PV and HG. The intestinal transit time (ITT, measured as ORTT – GTT) was <1.5 hr for VV and EF, and approximately 14 hr and 22 hr for PV and HG, respectively. These data suggest that the GTT of digesta as measured with BIPS was rapid for VV, EF, and HG. For VV and EF, the ORTT and ITT were also rapid, while for HG they were much slower. PV was characterized by delayed GTT, and a more rapid ITT compared to HG. Thus, patterns of flow for PV and HG, despite similar ORTT, differed in that HG emptied BIPS more rapidly and ITT was slower. The flow of BIPS did not differ for VV and EF. These data reveal new information in addition to the total tract transit time, and complement existing knowledge regarding anatomy and diet. Am. J. Primatol. 64:309–321, 2004. © 2004 Wiley‐Liss, Inc.
Integrierte Hybridsysteme aus Nanopartikeln und Biomolekülen: Synthese, Eigenschaften und Anwendungen
Authors: Katz Eugenii , Willner Itamar 
Published: November 2004

AbstractMetall‐ oder Halbleiter‐Nanopartikel und Nanostäbchen haben ähnliche Dimensionen wie Proteine (Enzyme, Antigene, Antikörper) oder DNA. Die Integration von Nanopartikeln (mit ihren besonderen elektronischen, photonischen und katalytischen Eigenschaften) mit Biomaterialien (mit ihren einzigartigen Erkennungsmechanismen sowie katalytischen und inhibierenden Fähigkeiten) ergibt hybride Nanobiomaterialien mit synergistischen Eigenschaften und Funktionen. Dieser Aufsatz beschreibt die aktuellsten Entwicklungen bei der Synthese von Hybridsystemen aus Biomolekülen und Nanopartikeln oder Nanostäbchen und deren Anwendung zum Aufbau von geordneten 2D‐ und 3D‐Strukturen in Lösung und auf Oberflächen. Schwerpunkte sind der Einsatz von Biomolekül‐Nanopartikel‐Konjugaten für die Bioanalytik sowie zur Herstellung bioelektronischer Funktionseinheiten und Nanoleiterbahnen aus Metall, Halbleitern oder magnetischen Materialien.
DNA Codes for Nanoscience
Authors: Samorì Bruno , Zuccheri Giampaolo 
Published: November 2004

AbstractThe nanometer scale is a special place where all sciences meet and develop a particularly strong interdisciplinarity. While biology is a source of inspiration for nanoscientists, chemistry has a central role in turning inspirations and methods from biological systems to nanotechnological use. DNA is the biological molecule by which nanoscience and nanotechnology is mostly fascinated. Nature uses DNA not only as a repository of the genetic information, but also as a controller of the expression of the genes it contains. Thus, there are codes embedded in the DNA sequence that serve to control recognition processes on the atomic scale, such as the base pairing, and others that control processes taking place on the nanoscale. From the chemical point of view, DNA is the supramolecular building block with the highest informational content. Nanoscience has therefore the opportunity of using DNA molecules to increase the level of complexity and efficiency in self‐assembling and self‐directing processes.
Oxorhenium Complexes as Aldehyde‐Olefination Catalysts
Authors: Santos Ana M. , Pedro Filipe M. , Yogalekar Ameya A. , Lucas Isabel S. , Romão Carlos C. , Kühn Fritz E. 
Published: November 2004

AbstractSeveral oxorhenium compounds in the formal oxidation states V and VII are examined as catalysts for the aldehyde‐olefination starting from diazo compounds, phosphines, and aldehydes. Of these, [ReMeO2(η2‐alkyne)] complexes provide the simplest catalysts to study, although [ReOCl3(PPh3)2] still remains the most efficient rhenium catalyst for aldehyde‐olefination described to date. Prior to the reaction with the Re catalysts the phosphine and the diazo compound react to form a phosphazine. No catalytic reaction occurs in cases where no phosphazine formation is observed. The first step of the catalytic cycle involves the formation of a carbene intermediate by the reaction of phosphazine and catalyst under extrusion of phosphine oxide and dinitrogen. In a second step the carbene reacts with aldehyde under olefin formation and catalyst regeneration. Excess of alkyne as well as the presence of ketones slows down the catalytic reaction. The olefination of 4‐nitrobenzaldehyde with diazomalonate is possible with these Re catalysts. In contrast, this reaction does not take place either in the classical Wittig fashion from Ph3PC(CO2Et)2 and aldehyde or by use of all other catalysts for aldehyde olefination reactions reported to date. Catalytic ylide formation from diazo compounds seems therefore not to be the only pathway through which catalytic aldehyde‐olefination reactions can proceed.
On the Role of PIII Ligands in the Conjugate Addition of Diorganozinc Derivatives to Enones
Authors: Pfretzschner Tatjana , Kleemann Lutz , Janza Birgit , Harms Klaus , Schrader Thomas 
Published: November 2004

AbstractA mechanistic study on the conjugate addition of diethylzinc to cyclohexenone catalyzed by various chiral PIII ligands, provides new insights into its mechanism. Complete in situ conversion of the catalytic amount of Cu(OTf)2 into CuI species by excess ZnEt2 is demonstrated by EPR spectroscopy. Experimental evidence is presented in favor of a critical ternary 1:1:1 complex between enone, Et2Zn and catalyst, supporting a rate‐limiting reductive elimination or carbocupration from a preformed mixed Cu/Zn cluster carrying one‐ or two‐ligand molecules. A crystal structure has been obtained for a CuI⋅L2 complex, which shows catalytic turnover on addition of reagent and substrate. NMR spectroscopic analyses and VT experiments reveal that steric hindrance may prevent complexation of a second ligand molecule on the CuI cation, leading to extremely fast precatalysts based on CuX⋅L species.