bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Variances at Different Significance Levels
Authors: de Ron A. M. , Ordas A. 
Published: May 2007

AbstractVariance components and their ratios broad‐sense heritability and constancy were estimated for some quantitative traits in northwestern Spain populations of maize. Estimations were carried out at the significance levels of 5% and 25% and without significance limits. It can be concluded that estimation without significance limits is more efficient than the estimations at the usual levels in the method of analysis of experimental data from fields experiments.
Single‐walled tubulin ring polymers
Authors: Boukari Hacène , Sackett Dan L. , Schuck Peter , Nossal Ralph J. 
Published: May 2007

AbstractAn unusual class of nanoscopic, ring‐shaped, single‐walled biopolymers arises when αβ‐tubulin is mixed with certain small peptides obtained from various marine organisms and cyanobacteria. The single‐ring structures, whose mean molecular weight depends on the specific peptide added to the reaction mixture, usually have sharp mass distributions corresponding, e.g., to rings containing eight tubulin dimers (when the added peptide is cryptophycin) and 14 dimers (e.g., with dolastatin). Although the ring‐forming peptides have been shown to possess antimitotic properties when tested with cultured eukaryotic cells (and thus have generated considerable interest as possible agents to be used in the treatment of cancer), it is not our intention to extensively discuss the potential pharmacological properties of the peptides. Rather, we will review the polymeric structures that form and illustrate how certain physical techniques can be used to characterize their properties and interactions. The nanoscopic size and particular geometry of the individual rings make them appropriate targets for scattering and hydrodynamic techniques that provide details about their structure in solution, but it is necessary to relate measured data to postulated structures by nontrivial, albeit straight‐forward, mathematical, and computational means. We will discuss how this is done when one uses such methods as small angle neutron scattering, dynamic light scattering, fluorescence correlation spectroscopy, and sedimentation velocity measurements. Moreover, we show that, by using several techniques, one can eliminate degeneracy to provide better discrimination between model structures. © 2007 Wiley Periodicals, Inc. Biopolymers 86: 424–436, 2007.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Reactions of tBu2AlH and RE(SiMe3)2 (R = H, SiMe3) – Synthesis and X‐ray Crystal Structures of [tBu2AlP(H)SiMe3]2 and [tBu2AlE(SiMe3)2]2 (E = Sb, Bi)
Authors: Matar Madhat , Kuczkowski Andreas , Keßler Ulrich , Schulz Stephan , Flörke Ulrich 
Published: May 2007

AbstractDehydrosilylation reactions between tBu2AlH and E(SiMe3)3 yielded the four‐membered heterocycles [tBu2AlE(SiMe3)2]2 (E = Sb, 1; Bi, 2), whereas no reaction was observed with P(SiMe3)3. In contrast, the reaction of tBu2AlH with HP(SiMe3)2 also proceeds with elimination of Me3SiH and subsequent formation of [tBu2AlP(H)SiMe3]2 (3). Complexes 1–3 were characterized by multinuclear NMR (1H, 13C{1H}, 31P{1H}) and mass spectroscopy, elemental analysis, andsingle‐crystal X‐ray diffraction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and Characterization of Iron, Cobalt, and Nickel Complexes Bearing Novel N,N‐Chelate Ligands and Their Catalytic Properties in Ethylene Oligomerization
Authors: Wang Li , Zhang Cheng , Wang Zhong‐Xia 
Published: May 2007

AbstractTreatment of o‐ROC6H4NC (R = PhCH2, iPr) with [Li{2‐CH(SiMe3)C5H4N}] afforded dimeric lithium complexes [Li{N(o‐ROC6H4)C(SiMe3)CH(2‐C5H4N)}]2 (3, R = PhCH2; 4, R = iPr). Reaction of the lithium complexes with 1 equiv. of (dme)NiCl2 gave nickel complexes [Ni{N(o‐ROC6H4)C(SiMe3)CH(2‐C5H4N)}2] (5, R = PhCH2; 6, R = iPr). The stoichiometric reaction of complexes 3 and 4 with Et3NH+Cl– formed 2‐{o‐ROC6H4NHC(SiMe3)CH}C5H4N (7, R = PhCH2; 8, R = iPr) in quantitative yields. Reaction of 7 or 8 with metal halides, including (dme)NiCl2, NiBr2, FeCl2·4H2O, and CoCl2 yielded complexes [MX2{(o‐ROC6H4)N=C(SiMe3)CH2(2‐C5H4N)}] (9, R = PhCH2, M = Ni, X = Cl; 10, R = iPr, M = Ni, X = Cl; 11, R = PhCH2, M = Ni, X = Br; 12, R = iPr, M = Ni, X = Br; 13, R = PhCH2, M = Fe, X = Cl; 14, R = iPr, M = Fe, X = Cl; 15, R = PhCH2, M = Co, X = Cl; 16, R = iPr, M = Co, X = Cl). For comparasion, nickel and cobalt complexes [MX2{(o‐MeC6H4)N=C(SiMe3)CH2(2‐C5H4N)}] (M = Ni, X = Br, 18; M = Co, X = Cl, 19) were similarly synthesized through reaction of 2‐{o‐MeC6H4NHC(SiMe3)CH}C5H4N (17) with NiBr2 and CoCl2, respectively. These compounds were characterized by NMR (for 3, 4, 7, 8, and 17) and IR (for 5–19) spectroscopy, elemental analyses and HRMS (for 5, 6, and 9–19). The molecular structures of complexes 3, 6, 12, and 14 were characterized by single‐crystal X‐ray diffraction techniques. The catalytic behavior in ethylene oligomerization of complexes 5, 6, 9–16, 18, and 19 was investigated. Under optimal conditions, the complexes showed good catalytic activities upon activation with appropriate aluminum co‐catalysts (8.72 × 102 to 18.2 × 102 kg/mol h atm for the nickel complexes upon activation with Et2AlCl and 4.3 × 102 to 8.1 × 102 kg/mol h atm for the iron and cobalt complexes upon activation with MMAO). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Cyclic Voltammetry in a Perfluorocarbon Emulsion Blood Substitute
Authors: Barlag Rebecca E. , Halsall H. Brian , Heineman William R. 
Published: May 2007

AbstractCyclic voltammetry in a perfluorocarbon emulsion based blood substitute (PEBS) was evaluated. The intent was to determine how PEBS affects the voltammetry of four representative electroactive compounds: potassium ferricyanide, ruthenium(II) trisbipyridine (rutris), hydroquinone, and 2,6‐dichloroindophenol (DCIP). Voltammograms in 0–20% PEBS‐Tris buffer mixtures are affected by PEBS, but reasonably well‐defined voltammograms are obtained in as much as 20% v/v. This report also shows that PEBS has only a small effect on amperometric detection of the reaction between DCIP and nicotinamide adenine dinucleotide (NADH), which has importance in clinical homogeneous immunoassays. Results support continued exploration of voltammetry/amperometry for quantitative analysis in this medium.
Determination of Cr(VI) in the Presence of Complexing Agents and Humic Substances by Catalytic Stripping Voltammetry
Authors: Grabarczyk Malgorzata , Kaczmarek Lukasz , Korolczuk Mieczyslaw 
Published: May 2007

AbstractThe voltammetric method of Cr(VI) determination in a flow system is proposed. Determinations can be carried out in the simultaneous presence of an excess of Cr(III), complexing agents, humic substances and surfactants. The method is based on the combination of a selective accumulation of the product of Cr(VI) reduction to the metallic state and a very sensitive voltammetric method of chromium determination in the presence of DTPA and nitrates. The calibration graph is linear from 1×10−9 to 5×10−8 mol L−1 for accumulation time of 30 s. The relative standard deviation is 5.2% (n=5) for Cr(VI) concentration 1×10−8 mol L−1. The influence of humic and fulvic acids, complexing agents and surfactants on Cr(VI) and the interfering Cr(III) signal is presented. The method was applied to Cr(VI) determination in certified reference material, soil sample, natural water sample and EDTA extracts from soil certified reference material.
Amperometric Urea Biosensor Using Aminated Glassy Carbon Electrode Covered with Urease Immobilized Carbon Sheet, Based on the Electrode Oxidation of Carbamic Acid
Authors: Wang Xiuyun , Watanabe Hiroaki , Sekioka Naoyuki , Hamana Hiroshi , Uchiyama Shunichi 
Published: May 2007

AbstractA large oxidation current can be observed when ammonium carbamate aqueous solution is electrolyzed using a glassy carbon electrode (GCE) at a potential exceeding 1.0 V vs. Ag/AgCl and amino groups are introduced at the surface of the GCE. Aminated GCE exhibits the electrocatalytic activity of the oxidation of ammonium carbamate that is produced from urea as an intermediate product of urease reaction, and a distinct oxidation current is observed when the aminated GCE is used to oxidize the urea in the urease solution. A novel amperometric determination method to detect urea has been developed. This method is based on the electrooxidation of carbamic acid produced during urease reactions. Urease is immobilized to polymaleimidostyrene (PMS) coated on the insulated amorphous carbon sheet set on the aminated GCE surface. A good linear relationship is observed between urea concentration and the electrolytic current of the urease‐immobilized electrode in the concentration range from 0.5 mM to 21.0 mM. The proposed urea biosensor has an effective merit in that the interference resulting from ammonia and pH change caused by the urease reaction can be eliminated, differing from conventional urea biosensors.
Comparative Studies of Tridentate Sulfur and Nitrogen‐Containing Ligands as Ionophores for Construction of Cadmium Ion‐Selective Membrane Sensors
Authors: Singh Ashok Kumar , Mehtab Sameena , Singh Udai P. , Aggarwal Vaibhave 
Published: May 2007

AbstractNew polymeric membrane cadmium‐ion selective sensors have been prepared by incorporating nitrogen and sulfur containing tridentate ligands as the ionophores into the plasticized PVC membranes. Poly(vinyl chloride) (PVC) based membranes of potassium hydrotris[N‐(2,6‐xylyl)thioimdazolyl) borate] (KTt2,6‐xylyl) and potassium hydrotris(3‐phenyl‐5‐methylpyrazolyl) borate (KTpPh,Me) with sodium tetraphenyl borate (NaTPB) as an anionic excluder and dibutylphthalate (DBP), tributylphthalate (TBP), dioctylsebacate (DOS), and o‐nitrophenyloctyl ether (o‐NPOE) as plasticizing solvent mediators were investigated in different compositions. KTt2,6‐xylyl was found to be a selective and sensitive ion carrier for Cd(II) membrane sensor. A membrane composed of KTt2,6‐xylyl:NaTPB:PVC:DBP with the % mole ratio 2.3 : 1.1 : 34.8 : 61.8 (w/w) works well over a very wide concentration range (7.8×10−8–1.0×10−2 M) with a Nernstian slope of 29.4±0.2 mV/decades of activity between pH values of 3.5 to 9.0 with a detection limit of 4.37×10−8 M. The sensor displays very good discrimination toward Cd(II) ions with regard to most common cations. The proposed sensor shows a short response time for whole concentration range (ca. 8 s). The effects of the cationic (tetrabutylammonium chloride, TBC), anionic (sodium dodecyl sulfate, SDS) and nonionic (Triton X‐100) surfactants were investigated on the potentiometric properties of proposed cadmium‐selective sensor. The proposed sensor based on KTt2,6‐xylyl ionophore has also been used for the direct determination of cadmium ions in different water samples and human urine samples.
Covalent Labeling of Nucleosides with VIII‐ and VI‐Valent Osmium Complexes
Authors: Trefulka Mojmír , Ostatná Veronika , Havran Luděk , Fojta Miroslav , Paleček Emil 
Published: May 2007

AbstractOsmium tetroxide complexes with nitrogen ligands [Os(VIII)L] have been widely applied as probes of the DNA structure and as electroactive labels of DNA. Here we describe the electrochemical behavior of Os(VIII)2,2‐bipyridine (Os, bipy)‐base‐labeled nucleosides. We show that electroactive label can be introduced also in the nucleoside ribose residues using six‐valent osmium complex. Cyclic voltammograms of sugar‐Os(VI)‐modified ribosides are similar but not identical to those of the base‐modified ribosides. Our results showing the electroactivity of sugar modified ribosides pave the way to facile end‐labeling of RNA.
DNA‐based nanofabrications
Authors: He Yu , Liu Haipeng , Chen Yi , Tian Ye , Deng Zhaoxiang , Ko Seung Hyeon , Ye Tao , Mao Chengde 
Published: May 2007

AbstractBeyond its biological importance, short DNA sequences are of increasing interest as excellent and versatile building blocks, in material science and nanotechnology. DNA nanotechnology has been rapidly developed and has branched into several significantly different directions. Controlling DNA nanostructures is one of the most important branches, in which well‐defined static nanostructures are constructed from rationally designed DNA motifs. The diversity and complexity of such DNA nanostructures also endow them with promising applications in nanofabrications, nanoelectronics, biodiagnostics, and DNA computations. In this review, we will summarize our recent efforts in this direction. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Microscopic measurement of the degree of mixing for nanoparticles in polymer nanocomposites by TEM images
Authors: Kim Dongsik , Lee Jun S. , Barry Carol M.F. , Mead Joey L. 
Published: May 2007

AbstractFor polymer nanocomposites, the small size of the fillers makes it difficult to analyze the degree of mixing quantitatively and often requires direct assessment via transmission electron microscopy (TEM). To date, qualitative comparisons and indirect measurements of the degree of mixing by measurement of certain properties are the most common methods. Better methods to quantitatively characterize the degree of mixing in nanocomposites would aid in studies investigating the effect of process conditions on the mixing behavior. Alumina/PET nanocomposites of identical composition, but with different degrees of mixing were prepared using a batch mixer. For evaluation of the degree of mixing with respect to both dispersion and distribution, three different techniques were applied and compared. TEM particle density was useful for dispersion, but did not adequately characterize distribution, while the Morisita's index gave poor results due to a wide range of effective particle sizes. Both methods ranked the samples differently compared to direct visual observation. In contrast, the skewness calculated by the quadrat method produced results consistent with visual rankings, and was found to be most effective in comparing and quantifying the degree of mixing. Although the quadrat method requires proper selection of quadrat size for a particular particle concentration, the skewness from the quadrat method was found to be most suitable as a standard index for the degree of mixing in nanocomposites. The usefulness of the quadrat method was verified using a second set of nanocomposites prepared by a twin screw extruder showing the potential for application of this technique for process development and quality control in commercial nanomanufacturing processes. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Self‐organized nanotemplating on misfit dislocation networks investigated by scanning tunneling microscopy
Authors: Diaconescu Bogdan , Nenchev Georgi , Jones Joshua , Pohl Karsten 
Published: May 2007

AbstractSelf‐ordering growth of nanoarrays on strained metallic interfaces is an attractive option for preparing highly ordered nanotemplates. The great potential of this natural templating approach is that symmetry, feature sizes, and density are predicted to depend on the interfacial stress in these strained layers, which can be adjusted by changing the substrate‐thin film composition, temperature, and adlayer coverage. This bottom‐up approach of growing nanostructured two‐dimensional ordered arrays of clusters on the misfit dislocation networks of strained metallic thin films and surfaces requires a detailed understanding of the nucleation and film–adsorbate interaction processes. Here we show how high resolution, large scale, variable temperature scanning tunneling microscopy imaging can improve our understanding of these self‐assembly processes. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Thermal, sonochemical, and mechanical behaviors of single crystal [60]fullerene nanotubes
Authors: Rauwerdink Kristen , Liu Jun‐Fu , Kintigh Jeremy , Miller Glen P. 
Published: May 2007

AbstractAlthough related to conventional carbon nanotubes in both shape and construction, fullerene nanowhiskers and fullerene nanotubes have received far less attention. A modified liquid–liquid interfacial precipitation technique is described to produce relatively uniform batches of [60]fullerene nanotubes in high yield. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) reveal that the tubes possess ∼100‐nm inside diameters and 300‐nm outside diameters. The [60]fullerene nanotubes degrade slowly at 180°C, eventually collapsing into micron scale [60]fullerene discs and rods, as revealed by optical microscopy and AFM. Ultrasonic cavitation chops [60]fullerene nanotubes into smaller segments within seconds. Longer ultrasonic bathing leads to considerable structural damage in which the sidewalls rupture. Mechanical stress tests using an AFM microscope tip effectively dent and break [60]fullerene nanowhiskers, revealing a hollow interior. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
An Overview of Nano‐Polymers for Orthopedic Applications
Authors: Balasundaram Ganesan , Webster Thomas J. 
Published: May 2007

AbstractThis review paper presents many exciting nanotechnology and tissue engineering approaches involving polymers that have enormous potential impact on human health care, particularly for orthopedic applications. As scaffolds play a vital role in tissue engineering, the feasibility of designing polymeric nano‐featured scaffolds is reviewed. Although bone is a very diverse tissue providing different functions within the body, recent work has resulted in new biomaterials with promise to solve orthopedic problems. Significant advancements in orthopedic care are required since recent data highlight a less than 15 year lifetime of current hip implants. Nanotechnology (or the use of nanomaterials) is providing a wide range of new materials to improve the current short lifetimes of orthopedic implants.magnified image
Bone Regeneration on Macroporous Aqueous‐Derived Silk 3‐D Scaffolds
Authors: Kim Hyeon Joo , Kim Ung‐Jin , Leisk Gary G. , Bayan Christopher , Georgakoudi Irene , Kaplan David L. 
Published: May 2007

AbstractSpinner flask culture under osteogenic conditions was used to study osteogenic outcomes from human bone marrow‐derived mesenchymal stem cells (hMSCs) seeded on aqueous‐derived porous silk scaffolds. Of particular novelty was the use of larger sized scaffolds (15 mm diameter, 5 mm thick) and large pore sizes (≈900–1 000 micron diameter). Cultures were maintained for 84 d in the spinner flasks and compared to static controls under otherwise similar conditions. The spinner flask cultures demonstrated enhanced cell proliferation compared to static cultures and the improved fluid flow promoted significantly improved osteogenic related outcomes based on elevated alkaline phosphatase (ALP) activity and the deposition of mineralized matrix. The expression of osteogenic differentiation associated markers based on real time PCR also demonstrated increased responses under the dynamic spinner flask culture conditions. Histological analysis showed organized bone‐like structures in the constructs cultured in the spinner flasks after 56 d of culture. These structures stained intensely with von Kossa. The combination of improved transport due to spinner flask culture and the use of macroporous 3D aqueous‐derived silk scaffolds with large pore sizes resulted in enhanced outcomes related to bone tissue engineering, even with the use of large sized scaffolds in the study. These results suggest the importance of the structure of the silk biomaterial substrate (water vs. solvent based preparation) and large pore sizes in improved bone‐like outcomes during dynamic cultivation.magnified image
A Cauchy integral formula for a class of elliptic systems of partial differential equations of first order in the space
Authors: Goldschmidt Bernd 
Published: April 2007

AbstractThis paper is a continuation of [6]. Here we construct a CAUCHYintegral formula and a POMPEJU‐representation for elliptic systems of partial differential equations of first order inRn, which may be described with the help of a CLIFFORD‐algebra. Moreover we study properties of the fundamental kernels and jump‐integrals.
On the index of degenerate pseudodifferential operators on a closed curve
Authors: Elschner Johannes 
Published: April 2007

AbstractWe consider a class of degenerate classical pseudodifferential operators on a closed curve and compute their index in Sobolev spaces. The index is expressed as a winding number by means of the principal and the subprincipal symbol. Furthermore, applications to the smoothness of solutions and the degenerate oblique derivative problem in the plane are given.
Cutting and Pasting of Elliptic Operators
Authors: Booss Bernhelm , Rempel Stephan 
Published: April 2007

AbstractIfA : C∞E → C∞Fis an elliptic operator between sections of vector bundlesE, Fover a closed smoothn‐manifoldX, Ya smooth (n– 1)‐submanifold ofXwith trivial normal bundle, and Ψ = (ΨE, ΨF) a pair of automorphisms ofE|YandF|Yinducing a diffeomorphismfofYand commuting with the principal symbol σAofAoverY, then an elliptic operatorAΨis (uniquely up to operators of lower order) defined between sections of vector bundlesEΨ,FΨover a closed manifoldXf, all obtained by cutting and pasting the respective objects alongY. The difference indexAΨ– indexAis investigated and the relations with additivity properties of topological invariants and with classical transmission problems are explained.
Short maximal chains in the lattice of clones over a finite set
Authors: Szendrei Ágnes 
Published: April 2007

AbstractLet ℒ︁k (3 ≦ k < ℵ0) denote the lattice of clones of finitary operations on a k‐element set. One interesting characteristic of the uncountable lattice ℒ︁k is the minimum lk of the cardinalities of maximal chains in ℒ︁k. It is known that for k prime lk = 5. In this paper the 5‐element maximal chains contained in ℒ︁k are investigated. It is proved that for k composite lk ≧ 6 while for k prime there are exactly (k–2)! (k + 4) 5‐element maximal chains in ℒ︁k, each closely related to a group operation.
Approximation of First Exit Times of Diffusions and Approximate Solution of Parabolic Equations
Authors: Platen Eckhard 
Published: April 2007

AbstractIn the paper the first exit time of a diffusion from a bounded region is approximated by first exit times of time discrete diffusion approximations. Their speed of convergence is estimated with respect to the maximum step size. Finally, this result is applied for the construction of approximate solutions of degenerate parabolic equations which can be used in Monte‐Carlo simulation algorithms.
On Spline Collocation for Singular Integral Equations
Authors: Schmidt G. 
Published: April 2007

AbstractThis paper is devoted to the approximate solution of one‐dimensional singular integral equations on a closed curve by spline collocation methods. As the main result we give conditions which are sufficient and in special cases also necessary for the convergence in SOBOLEV norms.The paper is organized as follows. In chapter 1 we indicate some definitions and some facts about projection methods. In chapter 2, we generalize a technique developed in [1] and study the convergence of collocations using splines of odd degree in periodic SOBOLEV spaces. In chapter 3, we apply our method to collocations by splines of even degree and consider the case of systems of equations. And in the last chapter, 4, the results are applied to singular integral equations and compared with known facts about piecewise linear spline collocation for such equations.