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Erich Kleinpeter - One of the best experts on this subject based on the ideXlab platform.

  • the Anisotropic Effect of functional groups in 1h nmr spectra is the molecular response property of spatial nics the frozen conformational equilibria of 9 arylfluorenes
    Tetrahedron, 2011
    Co-Authors: Erich Kleinpeter, Andreas Koch
    Abstract:

    Abstract Rotation about the single bond adjoining the aryl and fluorene moieties in 9-arylfluorenes can be frozen out on the NMR timescale if methyl groups are located at either one or both of the ortho positions of the aryl substituent. In the ground-state of these rotamers, the planes of the aryl and fluorene moieties are perpendicular to each other and the methyl substituents are consequently positioned either above the fluorene moiety or in-plane with it; thus, the methyl protons are either shielded or deshielded, respectively, due to the ring current Effect of the fluorene moiety. This Anisotropic Effect on the 1 H chemical shifts of the methyl protons has been quantified on the basis of through-space NMR shieldings (TSNMRS) and subsequently Δ δ calcd compared with the experimentally observed chemical shift differences, Δ δ exp . In this context, the experimental Anisotropic Effects of functional groups in the 1 H NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between Δ δ calcd and Δ δ exp were, for the first time, also quantified as arising from steric compression.

  • the Anisotropic Effect of functional groups in 1h nmr spectra is the molecular response property of spatial nucleus independent chemical shifts nics conformational equilibria of exo endotetrahydrodicyclopentadiene derivatives
    Organic and Biomolecular Chemistry, 2011
    Co-Authors: Erich Kleinpeter, Anica Lammermann, Heiner Kuhn
    Abstract:

    The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the Anisotropic Effects of the functional groups in the 1H NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS).

  • separation of Anisotropic and steric substituent Effects nuclear chemical shielding analysis of h 4 and c 4 in phenanthrene and 11 ethynylphenanthrene
    Journal of the American Chemical Society, 2004
    Co-Authors: Erich Kleinpeter, Sabrina Klod
    Abstract:

    The Anisotropic Effect of a proximally introduced ethynyl group on the chemical shifts of H-4 and C-4 of the phenanthrene skeleton was calculated using GIAO-HF/NICS methodology. The Anisotropic Effect, long considered to be the source of the considerable downfield shift of H-4 in 11-ethynylphenanthrene in comparison to the chemical shift value of the corresponding proton in phenanthrene, was determined to be only negligible in magnitude on the basis of these calculations. Partitioning of the natural chemical shieldings of H-4 and C-4 by the NCS-NBO method into various contributions from the C-C and C-H bonds present in each molecule revealed that steric compression was able to account for the large downfield shifts of both H-4 and C-4 in 11-ethynylphenanthrene relative to phenanthrene. Thus, the substituent Effect is almost totally permeated by this latter interaction and not by the aforementioned process, which was previously presumed to be the sole underlying cause.

  • ab initio quantum mechanical giao calculation of the Anisotropic Effect of c c and x c single bonds application to the 1h nmr spectrum of cyclohexane
    Journal of The Chemical Society-perkin Transactions 1, 2002
    Co-Authors: Sabrina Klod, Andreas Koch, Erich Kleinpeter
    Abstract:

    The Anisotropic Effects of the C–C single bond in ethane and various other X–C single bonds (X = OH, SH, NH2) have been quantitatively calculated as nuclear independent chemical shieldings (NICSs) in a three-dimensional grid of lattice atoms around the single bonds using the GIAO method integrated into the GAUSSIAN 98 calculation program. The shielding/deshielding areas due to the Anisotropic Effect have been plotted as iso-chemical-shift-surfaces (ICSSs); hereby, both direction and scale of the Anisotropic Effect were quantified and visualized. The results obtained are not in agreement with McConnell's point dipole model; the influence of the Anisotropic Effect of C–C and X–C single bonds on especially 1H chemical shifts must be reevaluated. The various magnetic contributions to the theoretical NMR shielding tensors of the axial/equatorial protons in cyclohexane were calculated by a detailed NCS-NBO analysis. The partition of the C(2)–C(3) [C(5)–C(6)] bonds at the C(1)–Hax/Hequ magnetic shielding tensors determines both position and chemical shift difference, dominated by hyperconjugation.

Heiner Kuhn - One of the best experts on this subject based on the ideXlab platform.

Yong Qing Fu - One of the best experts on this subject based on the ideXlab platform.

  • nebulization using zno si surface acoustic wave devices with focused interdigitated transducers
    Surface & Coatings Technology, 2019
    Co-Authors: Jian Zhou, Shurong Dong, Huigao Duan, Yifan Li, Yong Qing Fu
    Abstract:

    Abstract Propagation of surface acoustic waves (SAWs) on bulk piezoelectric substrates such as LiNbO3 and quartz, exhibits an in-plane Anisotropic Effect due to their crystal cut orientations. Thin film SAW devices, such as those based on ZnO or AlN, offer potential advantages, including isotropic wave velocities in all in-plane directions, higher power handling capability, and potentially lower failure rates. This paper reports experimental and simulation results of nebulization behaviour for water droplets using ZnO/Si surface acoustic wave devices with focused interdigital transducers (IDTs). Post-deposition annealing of the films at various temperatures was applied to improve the quality of the sputtering-deposited ZnO films, and 500 °C was found to be the optimal annealing temperature. Thin film ZnO/Si focused SAW devices were fabricated using the IDT designs with arc angles ranging from 30° to 90°. Nebulization was significantly enhanced with increasing the arc angles of the IDTs, e.g., increased nebulization rate, reduced critical powers required to initialise nebulization, and concentration of the nebulised plume into a narrower size of spray. Effects of applied RF power and droplet size have been systematically studied, and increased RF power and reduced droplet size significantly enhanced the nebulization phenomena.

Katya Rubia - One of the best experts on this subject based on the ideXlab platform.

  • meta analysis of fmri studies of disruptive behavior disorders
    American Journal of Psychiatry, 2016
    Co-Authors: Analucia A Alegria, Joaquim Radua, Katya Rubia
    Abstract:

    Objective:Functional magnetic resonance imaging (fMRI) studies in conduct disorder and in oppositional defiant disorder have shown inconsistencies. The aim of this meta-analysis of fMRI studies in disruptive behavior disorders was to establish the most consistent brain dysfunctions and to address task- and subtype-related heterogeneity.Method:Web-based publication databases were searched to conduct a meta-analysis of all whole-brain fMRI studies of youths with disruptive behavior disorder or conduct problems up to August 2015. Sub-meta-analyses were conducted in functional subdomains of emotion processing; in cool and hot executive functions, which refer to goal-directed higher cognitive functions with and without motivational and affective significance; and in a subgroup of youths with additional psychopathic traits. The authors performed a meta-analysis of voxel-based group differences in functional activation using the Anisotropic Effect-size version of seed-based d mapping.Results:Across 24 studies, 3...

  • gray matter abnormalities in childhood maltreatment a voxel wise meta analysis
    American Journal of Psychiatry, 2014
    Co-Authors: Lena Lim, Joaquim Radua, Katya Rubia
    Abstract:

    ObjectiveChildhood maltreatment acts as a severe stressor that produces a cascade of physiological and neurobiological changes that lead to enduring alterations in brain structure. However, structural neuroimaging findings have been inconsistent. The authors conducted a meta-analysis of published whole-brain voxel-based morphometry studies in childhood maltreatment to elucidate the most robust volumetric gray matter abnormalities relative to comparison subjects to date.MethodTwelve data sets were included, comprising 331 individuals (56 children/adolescents and 275 adults) with a history of childhood maltreatment and 362 comparison subjects (56 children/adolescents and 306 adults). Anisotropic Effect size-signed differential mapping, a voxel-based meta-analytic method, was used to examine regions of smaller and larger gray matter volumes in maltreated individuals relative to comparison subjects.ResultsRelative to comparison subjects, individuals exposed to childhood maltreatment exhibited significantly sm...

Darryll J Pines - One of the best experts on this subject based on the ideXlab platform.

  • guided wave phased array sensor based on a galfenol flake epoxy composite patch with unique circular comb pattern
    AIP Advances, 2019
    Co-Authors: Byungseok Yoo, Darryll J Pines
    Abstract:

    This paper investigates a study of the use of a Fe-Ga alloy (Galfenol) flake-epoxy composite patch with a circular comb shape for Magnetostrictive Phased Array Sensors (MPAS) used for Structural Health Monitoring (SHM) applications based on the ultrasonic Guided Wave (GW) inspection technique. Galfenol materials have demonstrated a variety of beneficial properties for transducer developments such as high magneto-mechanical coupling, low hysteresis loss, moderate magnetostriction and saturation magnetization, and steel-like manufacturability. However, typical Galfenol materials exhibit Anisotropic magnetostrictive characteristics that are disadvantageous for a wide range of applications to the GW SHM, especially phased array technology. To overcome the limitation of the Galfenol materials for the service of the GW phased array approach, we developed the Galfenol composite patch based on the circular comb pattern to improve the directional GW sensing performance using the shape Anisotropic Effect of the magnetostrictive material. The GW MPAS used in this work consists of a magnetostrictive composite patch directly bonded to a waveguide structure and a non-contact and azimuthally rotatable Hexagonal Magnetic Circuit Device (HMCD) including a biasing magnet and six sensing coils with predetermined directional sensing preferences. Although the GW signals obtained from the MPAS using the Galfenol composite patch were weak, the experimental results validated that the proposed MPAS was capable of detecting GWs using the flake-epoxy composite material and exhibited the obvious directional sensing characteristics. There are only six sensing coils in the HMCD, but the MPAS can acquire additional GW signal data in the Galfenol composite patch by simply altering the rotational orientation of the HMCD, leading to Effective array imaging results by suppressing unwanted shadow images induced by the side lobe Effect of the directional wavenumber filtering method.This paper investigates a study of the use of a Fe-Ga alloy (Galfenol) flake-epoxy composite patch with a circular comb shape for Magnetostrictive Phased Array Sensors (MPAS) used for Structural Health Monitoring (SHM) applications based on the ultrasonic Guided Wave (GW) inspection technique. Galfenol materials have demonstrated a variety of beneficial properties for transducer developments such as high magneto-mechanical coupling, low hysteresis loss, moderate magnetostriction and saturation magnetization, and steel-like manufacturability. However, typical Galfenol materials exhibit Anisotropic magnetostrictive characteristics that are disadvantageous for a wide range of applications to the GW SHM, especially phased array technology. To overcome the limitation of the Galfenol materials for the service of the GW phased array approach, we developed the Galfenol composite patch based on the circular comb pattern to improve the directional GW sensing performance using the shape Anisotropic Effect of the mag...

  • Guided wave phased array sensor based on a Galfenol flake-epoxy composite patch with unique circular comb pattern
    AIP Publishing LLC, 2019
    Co-Authors: Byungseok Yoo, Darryll J Pines
    Abstract:

    This paper investigates a study of the use of a Fe-Ga alloy (Galfenol) flake-epoxy composite patch with a circular comb shape for Magnetostrictive Phased Array Sensors (MPAS) used for Structural Health Monitoring (SHM) applications based on the ultrasonic Guided Wave (GW) inspection technique. Galfenol materials have demonstrated a variety of beneficial properties for transducer developments such as high magneto-mechanical coupling, low hysteresis loss, moderate magnetostriction and saturation magnetization, and steel-like manufacturability. However, typical Galfenol materials exhibit Anisotropic magnetostrictive characteristics that are disadvantageous for a wide range of applications to the GW SHM, especially phased array technology. To overcome the limitation of the Galfenol materials for the service of the GW phased array approach, we developed the Galfenol composite patch based on the circular comb pattern to improve the directional GW sensing performance using the shape Anisotropic Effect of the magnetostrictive material. The GW MPAS used in this work consists of a magnetostrictive composite patch directly bonded to a waveguide structure and a non-contact and azimuthally rotatable Hexagonal Magnetic Circuit Device (HMCD) including a biasing magnet and six sensing coils with predetermined directional sensing preferences. Although the GW signals obtained from the MPAS using the Galfenol composite patch were weak, the experimental results validated that the proposed MPAS was capable of detecting GWs using the flake-epoxy composite material and exhibited the obvious directional sensing characteristics. There are only six sensing coils in the HMCD, but the MPAS can acquire additional GW signal data in the Galfenol composite patch by simply altering the rotational orientation of the HMCD, leading to Effective array imaging results by suppressing unwanted shadow images induced by the side lobe Effect of the directional wavenumber filtering method