bluuebunny/crossref_metadata_2025_split huggingface dataset:
Random Computer Generation of 3D Molecular Structures: Theoretical and Statistical Analysis
Authors: Porquet Alain , Duval Jérôme F. L. , Buffle Jacques 
Published: February 2006

AbstractSummary: A computer program has been developed to generate three‐dimensional molecular structures randomly from a given collection of elementary chemical functional groups: the so‐called fragment database. The gradual assembly of the various fragments present in the database is performed according to a “self‐generation algorithm” (SGA). The latter is based on the covalent binding, step by step, between the unoccupied electronic valencies associated with the fragments of the database, and those of the growing molecular structure. When the number of electronic valencies of the molecular structure is zero, the growth process for this particular molecule is completed. It is shown that SGA is able to reproduce the asymmetric mass distributions of some natural colloids, like humic substances. In this article, particular attention is given to the analysis of the relationship existing between the fragment composition of the database and that of the collection of molecules generated. Mathematical expressions are derived and discussed, to understand the relationship between the proportions of the different types of fragments and the final composition of the generated molecular ensembles. For that purpose, a “pathway” formalism is proposed to describe exhaustively the whole set of generated molecules by specifying the distribution function of all of the fragments therein integrated. A statistical analysis that satisfactorily reproduces the predictions of the pathway model is extensively discussed.Example of a three‐dimensional structure obtained with the “self‐generation algorithm” (SGA).imageExample of a three‐dimensional structure obtained with the “self‐generation algorithm” (SGA).
Long‐term effects of bilateral subthalamic nucleus stimulation on health‐related quality of life in advanced Parkinson's disease
Authors: Siderowf Andrew , Jaggi Jurg L. , Xie Sharon X. , Loveland‐Jones Catherine , Leng Lewis , Hurtig Howard , Colcher Amy , Stern Matthew , Chou Kelvin L. , Liang Grace , Maccarone Heather , Simuni Tanya , Baltuch Gordon 
Published: February 2006

AbstractWe evaluated the long‐term effects of subthalamic nucleus (STN) stimulation on health‐related quality of life (HRQL) in patients with advanced Parkinson's disease (PD). STN stimulation improves motor function and decreases medication requirements in patients with advanced PD. The impact of STN stimulation on HRQL is less well established, especially beyond 1 year after surgery. We report HRQL outcomes for 18 patients with advanced PD. Patients were evaluated with the Parkinson's Disease Questionnaire‐39 (PDQ‐39), the Medical Outcome Study Short Form (SF‐36), and the EuroQol visual analogue scale (VAS) before surgery, 6 months postoperatively, and at a long‐term follow‐up visit (mean, 35.9 months; range, 18–57 months after surgery). Preoperative scores on HRQL measures were compared to results obtained at short‐ and long‐term follow‐up evaluations. The VAS and all domains of the PDQ‐39 except for cognition, communication, and social support showed marked improvements at 6 months after surgery. At the long‐term follow‐up, there were sustained improvements in the VAS (63% improvement; P = 0.0009) and in several domains of the PDQ‐39 [mobility: 20%, P = 0.01; activities of daily living (ADL): 29%, P = 0.005; emotional well‐being: 26%, P = 0.02; stigma: 43%, P = 0.003; and bodily discomfort: 35%, P = 0.007]. At the long‐term evaluation, only the vitality domain of the SF‐36 was significantly improved from baseline (16%; P = 0.01). In this selected group of patients, many of the short‐term gains in HRQL persist beyond 18 months after STN implantation. Benefits in nonmotor aspects of HRQL such as bodily discomfort and stigma appear to be among the most durable. © 2006 Movement Disorder Society
Fast Low‐Angle Dual Spin‐Echo (FLADE): A new robust pulse sequence for structural imaging of trabecular bone
Authors: Magland J. , Vasilic B. , Wehrli F. W. 
Published: February 2006

AbstractMechanical strength and fracture resistance of trabecular bone (TB) are largely determined by the structural arrangement of individual trabeculae. Fast 3D spin‐echo approaches are preferable to gradient echoes in that they are less sensitive to local induced gradients at the bone/marrow interface caused by magnetic susceptibility difference between the two tissues. FLASE is a 3D pulse sequence that serves this purpose. Here, we present a new pulse sequence dubbed FLADE (fast low‐angle dual spin‐echo) that overcomes some of the limitations inherent to FLASE, such as sensitivity to artifactual stimulated echoes. The double‐echo sequence features a flip angle <90 degrees allowing for TR ≪ T1. The second phase‐reversal pulse has the dual function of creating a second echo and restoring inverted longitudinal magnetization. The prolonged TR, made possible by sampling only half of kz‐space, is used to collect navigator echoes in adjacent slabs for sensing subpixel translational displacements. FLADE is shown to provide SNR comparable to FLASE while having narrower point‐spread function and being more robust to imperfections in the nonselective 180 degree pulses. Structural parameters derived from the in vivo images with the two pulse sequences are highly correlated, therefore suggesting that clinical data obtained with either pulse sequence can be merged. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
MR spectroscopic evidence for thalamic and hippocampal, but not cortical, damage in multiple sclerosis
Authors: Geurts Jeroen J. G. , Reuling Ilona E. W. , Vrenken Hugo , Uitdehaag Bernard M. J. , Polman Chris H. , Castelijns Jonas A. , Barkhof Frederik , Pouwels Petra J. W. 
Published: February 2006

AbstractGray matter (GM) damage is an important pathophysiological feature in Multiple Sclerosis (MS), and may be related to clinical, including cognitive, deficits. Quantitative single‐voxel 1H‐Magnetic Resonance Spectroscopy (TR/TE 6000/20 ms) was performed in 33 MS patients (11 per disease subtype; mean age 48 years, 16 females) and 10 healthy controls (mean age 43 years, 7 females). No overall spectroscopic changes were found in MS cortex. In MS thalamus, a 9% decrease of N‐acetyl aspartate (NAA; P = 0.005) and a 31% increase of myo‐inositol (Ins; P = 0.002) were found. A 21% Ins increase was observed (P = 0.02) in MS hippocampus. Reduced NAA and increased Ins concentrations are thought to reflect neuro‐axonal damage or loss and gliosis, respectively. Significant correlations between Ins concentrations and total‐brain T2 lesion load were found for MS thalamus (r = 0.65, P < 0.001) and hippocampus (r = 0.57, P = 0.001). MS thalamic and hippocampal Ins concentrations also correlated with each other (r = 0.68; P < 0.001). Cortical Gln correlated with thalamic NAA (r = −0.38; P = 0.03) in MS. Thalamic and hippocampal Ins increases were most prominent in secondary‐progressive (SP) patients (37% and 34%, respectively), whereas the largest thalamic NAA decrease (14%) was found in primary‐progressive (PP) patients. In conclusion, thalamic and hippocampal GM pathology are important features of (progressive) MS. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Oscillating steady states
Authors: Scheffler Klaus , Maderwald Stefan , Ladd Mark E. , Bieri Oliver 
Published: February 2006

AbstractThe signal formation and properties of steady‐state free precession (SSFP) in combination with alternating RF pulse phases or alternating spin precession is analyzed. Simulations and experiments demonstrate that the amplitudes of SSFP echo paths are significantly influenced by application of alternating phases either via the exciting RF pulse or via some external mechanism producing alternating spin precession. The influence of alternating phases on echo amplitudes is different for different echo paths. The primary SSFP echo paths F0− and F0+ exhibit a signal reduction whereas higher‐order echoes F−1− and F1+ show a signal increase upon application of oscillating phases. This behavior can be described using a simple perturbation theory applied to the frequency response profile of balanced SSFP combined with a final signal integration over one balanced SSFP band. The high sensitivity of SSFP echo amplitudes to alternating RF pulse phases or precession is exemplarily used to detect and visualize propagating transverse acoustic shear waves. Detection of flow or alternating currents are further possibilities to apply this unique feature of SSFP. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Automatic algorithm for correcting motion artifacts in time‐resolved two‐dimensional magnetic resoance angiography using convex projections
Authors: Raj Ashish , Zhang Honglei , Prince Martin R. , Wang Yi , Zabih Ramin 
Published: February 2006

AbstractTime‐resolved contrast enhanced magnetic resonance angiography (MRA) may suffer from involuntary patient motion. It is noted that while MR signal change associated with motion is large in magnitude and has smooth phase variation in k‐phase, signal change associated with vascular enhancement is small in magnitude and has rapid phase variation in k‐space. Based upon this observation, a novel projection onto convex sets (POCS) algorithm is developed as an automatic iterative method to remove motion artifacts. The presented POCS algorithm consists of high‐pass phase filtering and convex projections in both k‐space and image space. Without input of detailed motion knowledge, motion effects are filtered out, while vasculature information is preserved. The proposed method can be effective for a large class of nonrigid motions, including through‐plane motion. The algorithm is stable and converges quickly, usually within five iterations. A double‐blind evaluation on a set of clinical MRA cases shows that a completely unsupervised version of the algorithm produces significantly better rank scores (P = 0.038) when compared to angiograms produced manually by an experienced radiologist. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Structural topology optimization of vibrating structures with specified eigenfrequencies and eigenmode shapes
Authors: Maeda Y. , Nishiwaki S. , Izui K. , Yoshimura M. , Matsui K. , Terada K. 
Published: February 2006

AbstractIn vibration optimization problems, eigenfrequencies are usually maximized in the optimization since resonance phenomena in a mechanical structure must be avoided, and maximizing eigenfrequencies can provide a high probability of dynamic stability. However, vibrating mechanical structures can provide additional useful dynamic functions or performance if desired eigenfrequencies and eigenmode shapes in the structures can be implemented. In this research, we propose a new topology optimization method for designing vibrating structures that targets desired eigenfrequencies and eigenmode shapes. Several numerical examples are presented to confirm that the method presented here can provide optimized vibrating structures applicable to the design of mechanical resonators and actuators. Copyright © 2006 John Wiley & Sons, Ltd.
Flow feature aligned grid adaptation
Authors: Qin Ning , Liu Xueqiang 
Published: February 2006

AbstractA flow feature aligned grid adaptation method is proposed for the solution of Euler and Navier–Stokes equations for compressible flows, motivated by the desire for an efficient grid system for an accurate and robust solution method to best resolve flow features of interest. The method includes extraction of the flow features; generation of the embedded flow feature aligned structured blocks combined with unstructured grid generation for the rest of the flowfield; and adaptation of the hybrid grid for high flow feature resolution. The feature alignment makes it possible to maintain the high resolution property for both shock waves and shear layers of the approximate Riemann solvers and the higher order reconstruction schemes based on one‐dimensional derivation and dimensional splitting. High grid efficiency is obtained with highly anisotropic directional grid corresponding to the feature directions. The computational procedure is described in details in the paper and its application to flow solutions involving shock waves, boundary layers, wakes and shock boundary layer interaction are demonstrated. Its accuracy, efficiency and robustness are discussed in comparison with an anisotropic unstructured grid adaptations for the shock boundary layer interaction case. Copyright © 2006 John Wiley & Sons, Ltd.
A method for dynamic crack and shear band propagation with phantom nodes
Authors: Song Jeong‐Hoon , Areias Pedro M. A. , Belytschko Ted 
Published: February 2006

AbstractA new method for modelling of arbitrary dynamic crack and shear band propagation is presented. We show that by a rearrangement of the extended finite element basis and the nodal degrees of freedom, the discontinuity can be described by superposed elements and phantom nodes. Cracks are treated by adding phantom nodes and superposing elements on the original mesh. Shear bands are treated by adding phantom degrees of freedom. The proposed method simplifies the treatment of element‐by‐element crack and shear band propagation in explicit methods. A quadrature method for 4‐node quadrilaterals is proposed based on a single quadrature point and hourglass control. The proposed method provides consistent history variables because it does not use a subdomain integration scheme for the discontinuous integrand. Numerical examples for dynamic crack and shear band propagation are provided to demonstrate the effectiveness and robustness of the proposed method. Copyright © 2006 John Wiley & Sons, Ltd.
Organic light‐emitting diode (OLED) technology: materials, devices and display technologies
Authors: Geffroy Bernard , le Roy Philippe , Prat Christophe 
Published: February 2006

AbstractSince the breakthrough by Kodak in 1987, organic light‐emitting diodes (OLEDs) have been seen as one of the most promising technologies for future displays. A number of materials have been developed and improved in order to fulfil the requirements of this application. The materials differ from one another by their structure but also by the mechanism involved in the electroluminescence produced (fluorescence versus phosphorescence). When properly stacked, these materials result in a device that can achieve the required high efficiency and long lifetime. Such red, green and blue devices can then be combined in matrices to become the core of a display. Building up these structures onto a display backplane is one of the challenges facing the industry. The circuitry for driving the pixels can be adapted to the OLED, sometimes at the expense of the simplicity of the display, but bearing in mind that the fabrication process must remain industrially viable. Copyright © 2006 Society of Chemical Industry
Synthesis of styrene/methyl methacrylate copolymers by atom transfer radical polymerization: 2D NMR investigations
Authors: Brar A. S. , Puneeta  
Published: February 2006

AbstractCopolymers of styrene and methyl methacrylate were synthesized by atom transfer radical polymerization using methyl 2‐bromopropionate as initiator and CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as catalyst. Molecular weight distributions were determined by gel permeation chromatography. The composition of the copolymer was determined by 1H NMR. The comonomer reactivity ratios, determined by both Kelen–Tudos and nonlinear error‐in‐variables methods, were rS = 0.64 ± 0.08, rM = 0.63 ± 0.08 and rS = 0.66, rM = 0.65, respectively. The α‐methyl and carbonyl carbon resonances were found to be compositionally and configurationally sensitive. Complete spectral assignments of the 1H and 13C NMR spectra of the copolymers were done by distortionless enhancement by polarization transfer and two‐dimensional NMR techniques such as heteronuclear single quantum coherence and heteronuclear multiple quantum coherence. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2076–2085, 2006
Chemical preparation and characterization of new biodegradable aliphatic polyesters end‐capped with diverse steroidal moieties
Authors: Yang Jing , Li Qiaobo , Li Yang , Jia Lin , Fang Qiang , Cao Amin 
Published: February 2006

AbstractNovel metal complexes with a single catalytic site and less transesterification seem to provide alternative efficient synthetic approaches to preparing new biodegradable and biologically responsive materials with well‐defined structures. In this study, we rationally designed a new category of aluminum metal complexes bearing a bulky Salen ligand and diverse steroidal alkoxy moieties to synthesize novel biodegradable aliphatic polyesters end‐capped with steroidal building blocks. At first, three new aluminum metal complexes (9–11) were synthesized with good yields of 80–90%, bearing cholesterol and diosgenin derivatives as functional alkoxy moieties. By means of nuclear magnetic resonance (NMR) spectrometry, matrix‐assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI–FTMS), and Fourier transform infrared spectrometry, the molecular structures of 9–11 were characterized. Furthermore, new biodegradable aliphatic polyesters, poly(ε‐caprolactone) and poly(δ‐valerolactone) end‐capped with diverse steroidal moieties, were synthesized through the ring‐opening polymerization of ε‐caprolactone and δ‐valerolactone catalyzed by these new metal complexes under 100 °C in toluene, and they were also characterized by gel permeation chromatography, NMR, MALDI–FTMS, differential scanning calorimetry, and thermogravimetric analysis. Very narrow molecular weight distributions were revealed for these new polymer products, and their thermal crystallization and stability strongly depended on the degree of polymerization of the polyester building blocks and the distinct steroidal moieties. Because of the nature of the steroidal moieties, these biodegradable polymers may pave a path to new possibilities as potential biomaterials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2045–2058, 2006
Aromatic oxadiazole‐based conjugated polymers with excited‐state intramolecular proton transfer: Their synthesis and sensing ability for explosive nitroaromatic compounds
Authors: Kim Tae Hoon , Kim Hyung Jun , Kwak Chan Gyu , Park Won Ho , Lee Taek Seung 
Published: February 2006

AbstractAromatic polyoxadiazole derivatives containing 9,9′‐dioctylfluorene were successfully synthesized via the Suzuki coupling reaction. The oxadiazole moiety in the polymer backbone was linked with the bis(hydroxyphenyl) group in its 2‐position to exhibit a large Stokes shift in the emission spectrum due to the excited‐state intramolecular proton transfer. To prepare the polymer via the Suzuki cross‐coupling reaction, the hydroxyl group in the monomer was protected with the t‐butoxycarbonyl group before polymerization and removed after polymerization to a desirable extent. The polymer with the free hydroxyl group showed a considerable sensitivity for nitroaromatic compounds, exhibiting fluorescence quenching in a chloroform solution. The interaction between the electron‐donating OH group and electron‐deficient nitroaromatic compounds seemed to play a decisive role in fluorescence quenching. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2059–2068, 2006
Magneto‐Galvanic Effect in a Hollow Cathode Lamp: New Experimental Investigation
Authors: Slavov Dimitar , Petrov Lyubomir , Arsov Vladimir , Polischuk Vladimir , Mihailov Naiden , Todorov Georgi 
Published: February 2006

AbstractSummary: We report new experimental evidence of a magneto‐galvanic (MG) effect in commercial hollow cathode lamps (HCL). The goal of our investigation is to clarify the role of the neon 2p53s configuration in the formation of the MG signals. Our results eloquently relate the origin of the MG signal in the HCL discharge with the self‐alignment of the 1s5 metastable state. The observed destruction of the narrow resonance could be explained analogously to the optical depletion (“pumping‐off”) of the 1s5 metastable state.Comparison of the MG signals from the NeCu (triangles) and the NeCd (circles) lamps investigated here.imageComparison of the MG signals from the NeCu (triangles) and the NeCd (circles) lamps investigated here.
Deposition of CeO2 Films on Si(100) Substrates by Electron Beam Evaporation
Authors: Djanovski Georgi , Beshkova Milena , Velinova Sonia , Mollov Dimitar , Vlaev Petko , Kovacheva Daniela , Vutova Katia , Mladenov Georgi 
Published: February 2006

AbstractSummary: Thin films of cerium dioxide were deposited on silicon (100) substrates using e‐beam evaporation. The influence of different technological parameters, such as the substrate temperature, the oxygen pressure and the beam power on the crystallographic orientation of the films was explored. By optimizing these parameters, CeO2 thin films with a strongly preferred (200) orientation could be deposited on Si(100) substrates.XRD patterns of the CeO2 thin films deposited at various temperatures.imageXRD patterns of the CeO2 thin films deposited at various temperatures.
MNDO parameterized hybrid SLG/SCF method as used for molecular modeling of Zn(II) complexes
Authors: Darkhovskii M. B. , Tokmachev A. M. , Tchougréeff A. L. 
Published: February 2006

AbstractThe McWeeny's group functions technique is a natural way to introduce local description into quantum chemistry. It can also serve as a basis for constructing numerically effective computational schemes with almost linear scaling of computational costs with the size of a system. In this study, we apply it to the coordination compounds of Zn(II)‐containing ligands with nitrogen and oxygen donor atoms. In these compounds, the electron group corresponding to the metal vacant 4s‐ and 4p‐atomic orbitals (AOs) of the Zn2+ ion and its closest coordination sphere formed by the lone pairs (LP) located on the donor atoms naturally separates. This group, designated metal and lone pairs (MLP), is described by the SCF wave function within the hybrid scheme of strictly local geminals/self‐consistent field (SLG/SCF). The SLC/SCF scheme is based on the group function approach combining different descriptions for different electron groups: two‐electron two‐center bonds are described by geminals (SLG groups), while all the remaining electron groups are described by Slater determinants in the one‐electron (SCF) approximation (SCF groups). The original MNDO Hamiltonian parameterization for the Zn atom is adjusted for correct description of geometry of the complexes. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Conditions for accurate description of the electron density of atoms and molecules
Authors: Liu Shubin 
Published: February 2006

AbstractBased on the Kato's cusp condition of the electron density and our recent relations for local strongly decaying properties in an electronic system, necessary conditions for trial electron densities of atomic and molecular systems are derived. These conditions take the form of integral‐differential equations, and their validity is verified numerically. The relevance of these conditions to the Thomas–Fermi problem in the orbital‐less density functional approach is discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006