bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hochaufgelöste Kernresonanz‐Spektroskopie von Festkörpern. CP‐MAS‐NMR‐Spektroskopie
Authors: Wrackmeyer Bernd 
Published: December 2004

AbstractDie Kernresonanz‐Spektroskopie (Nuclear Magnetic Resonance = NMR)Vgl. diese Zeitschr. 1, 77, 116 (1967); 8, 44, 84 (1974); 16, 1, 35 (1982).
zählt aus folgenden Gründen zu den wichtigsten analytischen Methoden der modernen Chemie:
Sie ist in einem weiten Temperaturbereich (von ca. −190 bis + 300°C) anwendbar;
das zu untersuchende Material wird bei der Messung nicht zerstört;
sie liefert eine Fülle von chemisch und physikalisch relevanten Informationen;
sie läßt sich nicht nur in fast allen Bereichen der Grundlagenforschung der Naturwissenschaften anwenden, sondern es gibt auch zahlreiche industrielle Einsatzgebiete (z. B. Produktkontrolle); immer häufiger werden medizinische Fragestellungen (z. B. Tomographie, Krebsforschung) bearbeitet.
Der Siegeszug der NMR‐Spektroskopie begann mit der Herstellung kommerzieller NMR‐Geräte in den fünfziger Jahren nach den ersten erfolgreichen NMR‐Experimenten 1945/46.Vgl. diese Zeitschr. 20, 173 (1986).
Einige vereinfachte Grundlagen der NMR‐Experimente [1] sind in den Abbildungen 1 bis 4 dargestellt. Traditionell haben Chemiker bisher vor allem Flüssigkeiten oder gelöste Substanzen NMR‐spektroskopisch untersucht. Der Grund ist einfach: Die beiden im flüssigen Zustand leicht zugänglichen NMR‐Parameter „chemische Verschiebung”︁ δ und „Kopplungskonstante”︁ nJ(A−B) (n = Anzahl der Bindungen zwischen den Kernen A und B) lassen sich oft bequem und direkt in chemische Information umsetzen (Abbildung 5).
Die Alchemie im lateinischen Mittelalter. Ein Überblick
Authors: Weyer Jost 
Published: December 2004

AbstractAlchemie und Mittelalter – beides kommt dem Menschen von heute unendlich weit entfernt vor und ist doch in vielen Fällen näher, als er meint. So sind aus dem Mittelalter noch zahlreiche Bauwerke – Kirchen, Burganlagen und Bürgerhäuser – erhalten oder Institutionen wie die Klöster und die Universitäten. Weniger bekannt ist, daß auch von der Alchemie noch vieles in der heutigen Chemie wiederzufinden ist. Der Chemiker unserer Tage wird es nicht gern hören, wenn eine Verbindungslinie von der mittelalterlichen Alchemie zur modernen Chemie gezogen wird. Er braucht sich aber nicht zu schämen, daß zu seinen geistigen Vorfahren auch die Alchemisten gehören, denn es gab neben der Goldmacherei zu Betrugszwecken durchaus auch eine ernstzunehmende Alchemie. Dieser Alchemie verdankt die heutige Chemie vieles, ohne daß es dem Chemiker noch bewußt ist. Die folgende Aufzählung soll diese These belegen.
Kann man Chemische Bindungen sehen?
Authors: Boese Roland 
Published: December 2004

AbstractTeils, teils, müßte die diplomatische Antwort lauten, denn die Elektronen, die an einer chemischen Bindung beteiligt sind, können nicht unmittelbar abgebildet werden. Aber es gibt eine Methode, auf indirektem Weg aus experimentellen Daten die Elektronendichte zwischen Atomen zu ermitteln. Diese Methode soll in dem folgenden Aufsatz vorgestellt werden.
Ausrichtung und Orientierung von Molekülen. Neue Methoden zur Untersuchung von Elementarreaktionen
Authors: Rubahn Horst‐Günter 
Published: December 2004

AbstractDurch die Wechselwirkung mit starken elektromagnetischen Feldern können einzelne Moleküle in bezug auf einen Reaktionspartner ausgerichtet werden. Damit wird Information über den räumlichen (dreidimensionalen) Reaktionsablauf zugänglich. Im vorliegenden Beitrag geht es darum, was die Begriffe Orientierung und Ausrichtung einzelner Moleküle konkret bedeuten, wie sie zu erreichen sind und welchen Einfluß sie auf einfache Reaktionen haben.
Commitment of embryonic stem cells to an epidermal cell fate and differentiation in vitro
Authors: Troy Tammy‐Claire , Turksen Kursad 
Published: December 2004

AbstractThe epidermis develops from a stem cell population in the surface ectoderm that feeds a single vertical terminal differentiation pathway. To date, however, the limited capacity for the isolation or purification of epidermal stem or precursor cells has hampered studies on early commitment and differentiation events. We have developed a two‐step culture scheme in which pluripotent mouse embryonic stem (ES) cells are induced first to a surface ectoderm phenotype and then are positively selected for putative epidermal stem cells. We show that the earliest stages of epidermal development follow an ordered sequence that is similar to that observed in vivo (expression of keratin 8, keratin 19, keratin 17, and keratin 14), suggesting that ES cell‐derived surface ectoderm‐like cells can be induced to follow the epidermal developmental pathway. At a low frequency, keratin 14‐positive early epidermal cells progressed to keratin 1‐positive and terminally differentiated cells producing a cornified envelope. This culturing protocol provides an invaluable system in which to study both the mechanisms that direct stem cells along the epidermal pathway as well as those that influence their subsequent epidermal differentiation. Developmental Dynamics 232:293–300, 2005. © 2004 Wiley‐Liss, Inc.
The somite segmentation clock: It takes a licking and keeps on ticking
Authors: Kiefer Julie C. 
Published: December 2004

AbstractThis primer describes molecular mechanisms critical for somite segmentation clock function. In addition, two investigators of the segmentation clock, Olivier Pourquié, and Yun‐Jin Jiang, give their perspectives on current research and on the future of the field. Developmental Dynamics 232:519–523, 2005. © 2004 Wiley‐Liss, Inc.
OOPSE: An object‐oriented parallel simulation engine for molecular dynamics
Authors: Meineke Matthew A. , Vardeman Charles F. , Lin Teng , Fennell Christopher J. , Gezelter J. Daniel 
Published: December 2004

AbstractOOPSE is a new molecular dynamics simulation program that is capable of efficiently integrating equations of motion for atom types with orientational degrees of freedom (e.g. “sticky” atoms and point dipoles). Transition metals can also be simulated using the embedded atom method (EAM) potential included in the code. Parallel simulations are carried out using the force‐based decomposition method. Simulations are specified using a very simple C‐based meta‐data language. A number of advanced integrators are included, and the basic integrator for orientational dynamics provides substantial improvements over older quaternion‐based schemes. © 2004 Wiley Periodicals, Inc. J Comput Chem 26: 252–271, 2005
A free energy calculation study of the effect of H→F substitution on binding affinity in ligand–antibody interactions
Authors: Saito Minoru , Okazaki Isao , Oda Masayuki , Fujii Ikuo 
Published: December 2004

AbstractChanges in binding affinity to catalytic antibody 6D9 of chloramphenicol phosphonate derivatives (CPDs) containing H or F were investigated by performing free energy calculations based on molecular dynamics simulations. We calculated the binding free energy, enthalpy, and entropy changes (ΔΔG, ΔΔH, and −TΔΔS) attributable to H→F substitution by comparing results for CPDs containing a trifluoroacetylamino group (CPD‐F) or an acetylamino group (CPD‐H). The calculated ΔΔG, ΔΔH, and −TΔΔS values were −2.9, −6.3, and 3.5 kcal mol−1 and close to experimental values observed for a series of similar ligands, chloramphenicol phosphonates with F and H (−1.4, −3.5, and 2.1 kcal mol−1). Therefore, CPD‐F binds more strongly to 6D9 than does CPD‐H. To clarify the origin of the large difference in ΔΔG, we apportioned the calculated values of ΔΔG and ΔG for the associated and dissociated states into contributions from various atomic interactions. We found that the H→F substitution increased the binding affinity mainly by decreasing the hydration free energy and not by increasing favorable interactions with the antibody. The decreased hydration free energy of the ligand was mainly due to unfavorable coulombic interactions between the trifluoroacetylamino group and solvent waters, which increased the free energy of the dissociated state (by about 3.7 kcal mol−1). Also, the trifluoroacetylamino group slightly increased the free energy level of the associated state (about 0.8 kcal mol−1) because favorable van der Waals interactions compensated for unfavorable coulombic interactions with antibody atoms. In addition, the enthalpy and entropy changes, ΔΔH and −TΔΔS (computationally −6.3 and 3.5 kcal mol−1), originated mainly from a decrease in hydration free energy in the dissociated state. The CPD‐F and CPD‐H ligands had substantially different structures in the dissociated and complexed states. © 2004 Wiley Periodicals, Inc. J Comput Chem 3: 272–282, 2005
P2P‐R expression is genetically coregulated with components of the translation machinery and with PUM2, a translational repressor that associates with the P2P‐R mRNA
Authors: Scott Robert E. , White‐Grindley Erica , Ruley H. Earl , Chesler Elissa J. , Williams Robert W. 
Published: December 2004

AbstractP2P‐R is a nuclear protein with potential functional roles in the control of gene expression and mitosis. The P2P‐R protein also interacts with the p53 and Rb1 tumor suppressor proteins. To search for additional functional associations of P2P‐R, we employed the WebQTL database that contains the results of cDNA microarray analysis on forebrain, cerebellum, and hematopoietic stem cell (HSC) specimens of multiple BXD recombinant inbred strains of mice. Using WebQTL, gene products were identified that show genetically based coexpression with P2P‐R. Initial studies identified general groups of mRNAs that share common functional roles and high covariation in expression with P2P‐R. These functional groups involved the regulation of transcription, nucleotide binding, translation control, and ion transport. The findings related to translational mechanisms were further evaluated. In HSCs, expression of P2P‐R mRNA demonstrates an impressive expression correlation with a group of gene products associated with translation; high expression of P2P‐R specifically was associated with decreased expression of 29 ribosomal protein mRNAs. In all three tissues that were screened using the WebQTL database, a strong positive expression covariance between P2P‐R and the Pum2 gene product also was observed. PUM2 is a member of the highly conserved Puf family of RNA binding proteins that often function as gene‐specific translation regulators. The ability of Puf proteins to repress translation is mediated by their binding to specific elements located in the 3′ untranslated region (UTR) of their target mRNAs. To assess the functional significance of the strong genetic correlation in expression of P2P‐R and PUM2, the 3′ UTR of the P2P‐R mRNA was analyzed and found to contain one perfect consensus and two near‐perfect consensus PUM2 binding sequences. PUM2 pull‐down methods combined with reverse transcription and RT‐PCR confirmed that PUM2 does indeed bind P2P‐R mRNA. These results suggest that P2P‐R expression may be translationally regulated by PUM2 and that P2P‐R may modulate translation by influencing ribosomal protein gene expression. This study represents the first description of a RNA target for mammalian Puf proteins and the first molecular confirmation of information obtained using the WebQTL database. © 2004 Wiley‐Liss, Inc.
Diabetic fibrous mastopathy: Sonographic‐pathologic correlation
Authors: Baratelli Giorgio M. , Riva Cristina 
Published: December 2004

AbstractFibrous and inflammatory lesions of the breast in patients with early‐onset, longstanding insulin‐dependent diabetes mellitus (IDDM) can lead to misdiagnosis because the clinical, mammographic, and sonographic findings simulate breast cancer. We report a case of diabetic fibrous mastopathy with suspicious clinical, imaging, and cytologic findings. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 33:34–37, 2005
Reduction of artifacts by optimization of the sensitivity map in sensitivity‐encoded spectroscopic imaging
Authors: Zhao Xiaoli , Prost Robert W. , Li Zhu , Li Shi‐Jiang 
Published: December 2004

AbstractSensitivity‐encoded spectroscopic imaging (SENSE‐SI) reduces scanning time by using multiple coils for parallel signal acquisition. Significant artifacts could be induced by SENSE‐SI, mainly due to the low‐resolution nature of spectroscopic imaging. The present study introduces a novel method to reduce the artifacts. High‐resolution sensitivity maps are used in low‐resolution SENSE reconstruction. An intermediate unaliased image is obtained after SENSE reconstruction. Based on the intermediate image, the sensitivity maps are optimized and then the SENSE reconstruction is performed again. The final unaliased image has significantly reduced artifacts. Magn Reson Med 53:30–34, 2005. © 2004 Wiley‐Liss, Inc.
Simulation of High‐Frequency Atmospheric Gas Discharges
Authors: Zander Elmar , Weimar Jörg R. , Matthies Hermann G. 
Published: December 2004

AbstractThe generation of atmospheric gas discharges is an important concern in many industrial applications. We are investigating here a special type of high‐frequency atmospheric gas discharge. The results of modelling the breakdown mechanism and of the development phase of the discharge will be presented. Furthermore we will show first numerical results. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Implicit subgrid‐scale modeling by adaptive local deconvolution
Authors: Hickel Stefan , Adams Nikolaus A. 
Published: December 2004

AbstractA class of implicit Subgrid‐Scale (SGS) models for Large‐Eddy Simulation (LES) is obtained from a new approach for the finite‐volume discretization of hyperbolic conservation laws. The extension of a standard deconvolution operator and the choice of a suitable numerical flux function result in a truncation error which can be forced to have physical significance. As determined by a modified‐differential‐equation analysis, the free parameters of this implicit SGS model can be adjusted to approximate a known explicit SGS model. Computational results for the viscous Burgers equation show that the model with parameters identified by evolutionary optimization gives significantly better predictions than other models. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of turbulent diffusion in the temperature variance dissipation rate equation
Authors: Otić I. , Grötzbach G. 
Published: December 2004

AbstractResults of a new direct numerical simulation (DNS) for the Rayleigh‐Bénard convection at Prandtl number Pr = 0.025 and Rayleigh number Ra = 100,000 are used to analyse the turbulent diffusion term in the transport equation for the temperature variance dissipation rate. These DNS results are also used to investigate the performance of statistical models for this turbulent diffusion term. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of compact upwind‐biased finite‐difference schemes forfeedback‐coupled advection equations
Authors: Jocksch A. , Adams N. A. , Kleiser L. 
Published: December 2004

AbstractA fifth‐order compact upwind‐biased finite‐difference scheme has been developed which is asymptotically stable when applied to linear 2 × 2 systems. This scheme was optimised with respect to wave propagation through the boundaries. In order to achieve asymptotic stability for such systems a sufficient stability condition, based on the Nyquist criterion of linear system theory, was included in the optimisation as additional constraint. The evaluation of the stability condition was done numerically. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of computational aeroacoustics with theory using the benchmark case of sound waves excited from a semi‐infinite duct
Authors: Morgenweck Daniel , Schemel Christoph , Thiele Frank 
Published: December 2004

AbstractIn this paper the benchmark problem of radiation from a semi infinite duct is discussed. The duct is modeled by an infinitesimal thin wall. Comparisons are made between the analytic solutions of R. M. Munt and the 2nd CAAWorkshop with our CAA‐code. In all cases a 3D axisymmetric approach is chosen to describe the propagation of a single mode. The procedure consists of two steps. Step 1 concerns a numerical simulation of the near‐field‐region. Step 2 calculates the farfield‐solution by means of the acoustic‐analogy of FfowcsWilliams and Hawkings. Since the wall is of infinitesimal thickness, the edge needs to be treated in a special way. Two different approaches are persecuted and the results are compared. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Buckling localization in a non‐elastic rotating disk
Authors: Alexandrova Nelli N. , Vila Real Paulo M. M. 
Published: December 2004

AbstractBuckling localization of a rotating disk made of elastic‐perfectly plastic material is investigated using stress‐rate formulation of the stability boundary‐value problem. The phenomenon of plastic buckling localization and its analogy with elastic buckling localization is discussed. For a thin rotating disk, it is shown that buckling develops at a speed lower than one at which the disk passes to fully plastic state, or in other words, before the limit load has been attained. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical bifurcation analysis of a ‘car‐following’ model
Authors: Sirito Gabriele , Gasser Ingeniun , Seidel Tilman 
Published: December 2004

AbstractWe study a system of ordinary differential equations describing a car‐following model for the motion of N car around a circular highway. All cars behave in the same way. The acceleration of each car is determined as a function of the headway (optimal velocity function). This model is known to have a solution with constant velocities and headways which, in a certain parameter regime, is stable and, varying the density of the cars, the loss of stability is generally due to a super‐ or subcritical Hopf bifurcation. Guided by analytical results, we numerically investigate the global bifurcation diagram for periodic solutions and obtain a complete picture of the dynamics of the model. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational model for adaptive fiber‐strengthened endothelial cell layers under flow induced shear‐stress
Authors: Buschmann M. H. , Schnittler H. J. , Adams N. A. 
Published: December 2004

AbstractEndothelial cells, covering the inner surface of human vessels and the heart are permanently exposed to fluid shear stress which strongly affects endothelial structure and function. Due to their location at the interface between blood‐flow and the vascular wall endothelial cells play an essential role in hemodynamics. We present a complex computational model based on the Navier‐Stokes equations, Donell's shell equations, and additional constitutive systems of equations for the description of the flow around and inside of endothelial cells. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localization and Pattern Formation in BBGKY Hierarchy
Authors: Fedorova Antonina N. , Zeitlin Michael G. 
Published: December 2004

AbstractA fast and efficient numerical‐analytical approach is proposed for modeling complex behaviour in the BBGKY hierarchy of kinetic equations. Numerical modeling shows the creation of various internal structures from localized modes, which are related to the localized or chaotic type of behaviour and the corresponding patterns (waveletons) formation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Steady Groundwater Flow with Steep Gradients: An Analytic Approach to the 2D–Problem with a Vertical Pressure Boundary Condition and Steady Recharge/Drainage
Authors: Fröhner Anja , Edenhofer Johann , Schmitz Gerd H. 
Published: December 2004

AbstractSteady groundwater flow with steep gradients in a vertical plane due to superficial recharge/drainage, inner sources/sinks and a one‐sided pressure boundary condition can be described by a 2D Poisson equation with a nonlinear free surface boundary condition. By means of conformal mapping techniques Schmitz and Edenhofer [1] derived the exact explicit solution of this problem in a horizontally infinite aquifer. Their results are extended to problems with a one‐sided vertical pressure boundary condition, modelling f. ex. the boundary between an aquifer and an adjacent free water body. According to ist simple parametrization, this approach can be applied on one hand to model various real world phenomena like river–aquifer–systems. It may on the other hand serve as a tool for investigating the exactness of numerical solutions and the range of validity of simplifying assumptions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local existence of the solution to the initial‐boundary value problem in nonlinear thermomicroelasticity theory
Authors: Gawinecki Jerzy , Łazuka Jarosław 
Published: December 2004

AbstractWe prove a theorem about local existence (in time) of the solution to the first initial‐boundary value problem for a nonlinear system of equation of the thermomicroelasticity theory. At first, we prove existence, uniqueness and regularity of the solution to this problem for the associated linearized system by using the method of semi‐group theory. Next, basing on this theorem, we prove an energy estimate for the solution to the linearized system by applying the method of Sobolev space. At the end, using the Banach fixed point theorem, we prove that the solution of our nonlinear problem exists and is unique. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a Model for Fires in Tunnel Network Structures
Authors: Kraft Marcus , Gasser Ingenuin 
Published: December 2004

AbstractA one dimensional model to describe the dynamics of tunnelfires is used to model tunnel network structures. The corresponding conditions at the nodes are formulated. A numerical methods is presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Drobot's algebraic theory of dimensional analysis in construction of system of mechanoelectric analogies. Application to the problems of acoustoelectric waves propagation in porous long bones
Authors: Uklejewski R. , Czapski T. 
Published: December 2004

AbstractBasing on the algebraic theory of dimensional analysis given by S. Drobot [3] and extended by A. Muciek [4], the definition of a system of mechano–electric analogies has been proposed as an isomorphism of dimensional subspaces: of all the mechanic quantities Πm and of all the electric quantities Πe. The method of construction of systems electromechanical analogies has been given and applied to the problems of acousto–electric waves propagation in porous long bones in order to derive an unified method of analysis of these problems by means of the methods used in the electric transmission line theory. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Binary Mixtures in Bayesian Treatment
Authors: Boese F. G. 
Published: December 2004

AbstractIn the Bayesian treatment of binary statistical mixture distributions, also an integration with respect to the mixture parameter is to be carried out. An exact integral evaluation is devised to effectuate this integration fast and numerically stable. On an astronomical application to Bayesian source detection in x‐ray photon data from the ROSAT all–sky survey is reported. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reliability of Elastic‐Plastic Frame Structures
Authors: Sieniawska Roza , Wysocka Alina , Zukowski Stanislaw 
Published: December 2004

AbstractAn effective algorithm for estimating the reliability of frame structures made of an elastic perfectly plastic material is presented. It is assumed that the structure is working in uniaxial state of stress, the material parameters and the limit values of the loads are described by random variables, all loads are acting in a static manner, the probability density functions of all random variables, which describe the structure and loads are known. As the structure reliability measure the probability of failure and corresponding reliability index are regarded. The dead (constant) load and the climatic loads are taken into account. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)