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21.
The low velocity and low energy impact response of two common sheet mold compound (SMC) material systems—SMC-R27, and SMC-R37—were
investigated. In addition to characterizing the low velocity impact response and failure progression of the material systems,
the edge effects of diamond saw cutting, waterjet cutting and abrasive waterjet cutting were investigated using optical microscopy
and contact surface profilometry. Impact force–time and displacement–time responses were measured and used to characterize
energy absorption capabilities and potential correlation to post processing operation and fiber volume fraction. Pre and post-impact
edge surface micrographs were examined to relate the failure behavior on the machined surfaces. Experiments and measurements
all show that the failure zone size and growth behavior are clearly dependent on the edge finishing process. 相似文献
22.
Marc B. Taraban Daniel J. Deredge Margaret E. Smith Katharine T. Briggs Yu Li Zhong-Xing Jiang Patrick L. Wintrode Yihua Bruce Yu 《Magnetic resonance in chemistry : MRC》2019,57(10):861-872
The conformational transition of a fluorinated amphiphilic dendrimer is monitored by the 1H signal from water, alongside the 19F signal from the dendrimer. High-field NMR data (chemical shift δ, self-diffusion coefficient D, longitudinal relaxation rate R1, and transverse relaxation rate R2) for both dendrimer (19F) and water (1H) match each other in detecting the conformational transition. Among all parameters for both nuclei, the water proton transverse-relaxation rate R2(1H2O) displays the highest relative scale of change upon conformational transition of the dendrimer. Hydrogen/deuterium-exchange mass spectrometry reveals that the compact form of the dendrimer has slower proton exchange with water than the extended form. This result suggests that the sensitivity of R2(1H2O) toward dendrimer conformation originates, at least partially, from the difference in proton exchange efficiency between different dendrimer conformations. Finally, we also demonstrated that this conformational transition could be conveniently monitored using a low-field benchtop NMR spectrometer via R2(1H2O). The 1H2O signal thus offers a simple way to monitor structural changes of macromolecules using benchtop time-domain NMR. 相似文献
23.
The appearance of body-frame singularities in gauge potentials when three collective angles are separated by means of Wigner D-functions is a fundamental difficulty in the quantum N-body problem. We show that the use of the overcomplete basis of minimal multipolar harmonics allows these singularities to be avoided at the expense of increasing the dimension of the resulting system of coupled equations describing the internal motion of the system. 相似文献
24.
Thermal degradation of 1,2-bis(dichloroboryl)ethane gives low yields of a white solid (BCl)6(CH)4 which has a hexaboro-adamantane structure. Substitution of the chlorine atoms by bromine or methyl occurs on treatment with BBr3 and Sn(CH3)4, respectively. 相似文献
25.
Biancardo M Quinn AJ Floyd L Mendes PM Briggs SS Preece JA Bignozzi CA Redmond G 《The journal of physical chemistry. B》2005,109(18):8718-8722
We report on charge transport measurements through laterally contacted assemblies of Au nanoparticles capped with 11-mercaptoundecanoic acid ligands. Both alternating- and direct-current data indicate that although the nanoparticles behave as electrically isolated metallic islands, there is a significant influence from the nanoparticle environment, indicating the existence of a slow reorganization process linked to charge transport. On the basis of the observation of temperature-dependent hysteresis of charge tunneling, we propose that this process is due to proton transfer between the carboxylic acid tails of the ligands. 相似文献
26.
Morton JJ Tyryshkin AM Ardavan A Porfyrakis K Lyon SA Briggs GA 《Physical review letters》2005,95(20):200501
Systematic errors in spin rotation operations using simple rf pulses place severe limitations on the usefulness of the pulsed magnetic resonance methods in quantum computing applications. In particular, the fidelity of quantum logic operations performed on electron spin qubits falls well below the threshold for the application of quantum algorithms. Using three independent techniques, we demonstrate the use of composite pulses to improve this fidelity by several orders of magnitude. The observed high-fidelity operations are limited by pulse phase errors, but nevertheless fall within the limits required for the application of quantum error correction. 相似文献
27.
Background
Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH. 相似文献28.
A random network model containing defects has been developed and applied to the deposition of amorphous SiOx films on a flat substrate. A new Monte Carlo procedure enables dangling bonds to migrate and annihilate. The degree of porosity in the films is found to increase with oxygen content. As the oxygen content increases a larger fraction of pore surfaces is covered with oxygen, and the density of dangling bonds on pore surfaces decreases. Oxygen plays the role of a surfactant, lowering the energies of pore surfaces and enhancing the porosity of amorphous SiO2 compared to amorphous Si. 相似文献
29.
15N n.m.r. spectra have been recorded from salts of 15N enriched ammonium ions in aqueous solution. Shifts of the resonance frequency have been attributed to direct interaction between the ammonium and its counter ion in solution. 相似文献
30.
Gimenez-Lopez Mdel C Räisänen MT Chamberlain TW Weber U Lebedeva M Rance GA Briggs GA Pettifor D Burlakov V Buck M Khlobystov AN 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):10977-10985
Anisotropy of intermolecular and molecule-substrate interactions holds the key to controlling the arrangement of fullerenes into 2D self-assembled monolayers (SAMs). The chemical reactivity of fullerenes allows functionalization of the carbon cages with sulfur-containing groups, thiols and thioethers, which facilitates the reliable adsorption of these molecules on gold substrates. A series of structurally related molecules, eight of which are new fullerene compounds, allows systematic investigation of the structural and functional parameters defining the geometry of fullerene SAMs. Scanning tunnelling microscopy (STM) measurements reveal that the chemical nature of the anchoring group appears to be crucial for the long-range order in fullerenes: the assembly of thiol-functionalized fullerenes is governed by strong molecule-surface interactions, which prohibit formation of ordered molecular arrays, while thioether-functionalized fullerenes, which have a weaker interaction with the surface than the thiols, form a variety of ordered 2D molecular arrays owing to noncovalent intermolecular interactions. A linear row of fullerene molecules is a recurring structural feature of the ordered SAMs, but the relative alignment and the spacing between the fullerene rows is strongly dependent on the size and shape of the spacer group linking the fullerene cage and the anchoring group. Careful control of the chemical functionality on the carbon cages enables positioning of fullerenes into at least four different packing arrangements, none of which have been observed before. Our new strategy for the controlled arrangement of fullerenes on surfaces at the molecular level will advance the development of practical applications for these nanomaterials. 相似文献