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1.
Magnetic-Bottle and Velocity-Map Imaging Photoelectron Spectroscopy of APS- (A=C14H10 or Anthracene): Electron Structure,Spin-Orbit Coupling of APS·, and Dipole-Bound State of APS-
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Qin-qin Yuan Zheng Yang Ren-zhong Li Wesley J. Transue Zhi-peng Li Ling Jiang Niranjan Govind Christopher C. Cummins Xue-Bin Wang 《化学物理学报(中文版)》2018,31(4):463-470
Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS-(A=C14H10 or anthracene) were generated via electrospray ionization, and characterized by magnetic-bottle photoelectron spectroscopy, velocity-map imaging (VMI) photoelectron spectroscopy, and quantum chemical calculations. The electron affinity (EA) and spin-orbit (SO) splitting of the APS· radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA=(2.62±0.05) eV and SO splitting=(43±7) meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy (eKE) of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31++G(d, p) calculations indicate APS· has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron. 相似文献
2.
Magnetic resonance imaging (MRI) is a non-invasive and non-optical measurement technique, which makes it a promising method for studying delicate and opaque samples, such as foam. Another key benefit of MRI is its sensitivity to different nuclei in a sample. The research presented in this article focuses on the use of MRI to measure density and velocity of foam as it passes through a pipe constriction. The foam was created by bubbling fluorinated gas through an aqueous solution. This allowed for the liquid and gas phases to be measured separately by probing the 1H and 19F behavior of the same foam. Density images and velocity maps of the gas and liquid phases of foam flowing through a pipe constriction are presented. In addition, results of computational fluid dynamics simulations of foam flow in the pipe constriction are compared with experimental results. 相似文献
3.
《Comptes Rendus de l'Academie des Sciences Series IIC Chemistry #》1998,326(11):705-710
With the use of 25 images per s camera, the process of solid plugs of a gas-solid plug flow in a pipe bend with constant curvature (Rb/D=0) can be highlighted. This process can be seen on frame sequences 1, 2, 3 and 4. This study is realised in horizontal-vertical pipes, for solid-gas mass flow rates (q=qs/qg) equal to 12.7 and 17.9. The visualisations show that the flow deceleration and propulsion stages of the solid plug are not correlated because at the end of the deceleration stage, the plug velocity is zero. This work has allowed us to validate the different hypotheses necessary for the stress model between solid plug and the outer face of a pipe bend. 相似文献
4.
Xin‐Gui Li Hai‐Jun Zhou Mei‐Rong Huang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(23):6109-6124
Copolymers were synthesized through the chemically oxidative polymerization of N‐ethylaniline (EA) and aniline (AN) in five acid aqueous media. The polymerization yield, intrinsic viscosity, molecular weight, solubility, solvatochromism, electrical conductivity, and mechanical properties of the copolymer films were systematically studied through changes in the comonomer ratio, polymerization temperature, oxidant, oxidant/monomer ratio, and acid medium. Open‐circuit‐potential and temperature measurements of the polymerization solutions showed that the polymerization rate depended on the EA content, and the polymerization was an exothermic reaction. The resultant copolymers were characterized in detail with IR, ultraviolet–visible, and 1H NMR spectroscopy, gel permeation chromatography, wide‐angle X‐ray diffractometry, and scanning electron microscopy. The reactivity ratios of the monomer pair were calculated from the 1H NMR spectra of the copolymers formed at a low conversion. The polymers exhibited good solubility and interesting solvatochromism in most of the solvents and variable conductivity with the EA/AN ratio and doping state. The conductivity of the HCl‐doped copolymers increased monotonically from 5.61 × 10?7 to 2.55 × 10?1 S/cm with decreasing EA content from 100 to 0 mol % and showed a percolation transition between EA concentrations of 20 and 30 mol %. The EA/AN copolymers also had excellent film formability and flexibility together with high mechanical and oxygen‐enriching properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6109–6124, 2004 相似文献
5.
A Hyperpolarizable 1H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage
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Dr. Soumya S. Roy Dr. Philip Norcott Dr. Peter J. Rayner Prof. Dr. Gary G. R. Green Prof. Dr. Simon B. Duckett 《Angewandte Chemie (International ed. in English)》2016,55(50):15642-15645
Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are two extremely important techniques with applications ranging from molecular structure determination to human imaging. However, in many cases the applicability of NMR and MRI are limited by inherently poor sensitivity and insufficient nuclear spin lifetime. Here we demonstrate a cost‐efficient and fast technique that tackles both issues simultaneously. We use the signal amplification by reversible exchange (SABRE) technique to hyperpolarize the target 1H nuclei and store this polarization in long‐lived singlet (LLS) form after suitable radiofrequency (rf) pulses. Compared to the normal scenario, we achieve three orders of signal enhancement and one order of lifetime extension, leading to 1H NMR signal detection 15 minutes after the creation of the detected states. The creation of such hyperpolarized long‐lived polarization reflects an important step forward in the pipeline to see such agents used as clinical probes of disease. 相似文献
6.
BorECO®™ BA212E is a polypropylene block co-polymer which has become a common material in the manufacturing of large diameter non-pressurized gravity offshore intake pipelines. These lines are used for transportation of sea water for cooling of petrochemical process plants. The pipe sections are joined by butt heat fusion welding to create the pipeline. Recently a few premature failures of such pipelines have been reported in the field. Hence, there is a need to characterize the constitutive behavior of the pipe and weld material in order to properly design these pipes. The aim of this work is to determine the material constitutive behaviors of the pipe material and the welded joint material. Uniaxial tensile tests of both the pipe and weld joint material are conducted at various strain rates. Both the pipe and weld material show a rather high strain rate dependency, with the weld material having about half the yield strength than that of the pipe material. An analytical constitutive material model is developed for both the pipe and weld material, incorporating the effect of strain rate. The failure locus, expressed in terms of the equivalent plastic strain at failure vs. the stress triaxiality, for both materials is also determined as part of the constitutive model using notched dumbbell specimens. The constitutive model and failure loci for the pipe and weld material are implemented in a finite element model (FEM) and are validated by conducting a series of independent four-point bend experiments on both material types. The validation is carried out by comparing the FEM results of the four-point bend model with the experimental results, which show a rather good agreement. 相似文献
7.
Pablo Trigo‐Mouriño Christian Merle Martin R. M. Koos Prof. Burkhard Luy Prof. Roberto R. Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7013-7019
Deuterium NMR imaging was used to evaluate the spatial distribution of the degree of alignment in different types of alignment media by monitoring the deuterium quadrupolar splitting using spatially resolved NMR techniques in conventional liquid state NMR instruments. These images allow the unambiguous distinction of magnetic field and alignment inhomogeneities present in partially aligned samples, revealing the underlying reasons for linebroadening within an alignment medium that cannot be explained by the sole analysis of 1D 2H NMR spectra. For example, alignment inhomogeneities due to broken gels or the presence of concentration gradients in liquid crystalline solutions are clearly detected by the imaging methods proposed in this work. 相似文献
8.
Pipes consisting of layers of different materials (multilayer pipes) are considered. The fracture toughness value of the main pipe is taken into account as a parameter relevant to fracture assessment connected with the resistance of pipe material against slow crack growth. With the aim of simplifying estimation of main pipe material fracture toughness, non-homogeneous test specimens cut directly from multi-layer pipes are suggested and numerically analysed. The values of the corresponding stress intensity factor KI and biaxiality factors B are calculated for the case of two and three layer test specimens. Based on the results obtained, the transferability of fracture toughness values measured on laboratory specimens to pipe systems is discussed. It is shown that in most cases of multi-layer commercial pipes and routine fracture toughness measurements the values of the stress intensity factor calculated on the basis of homogeneous specimens can be used. 相似文献
9.
Steven E. Kirberger Sofia D. Maltseva Joseph C. Manulik Dr. Samuel A. Einstein Dr. Bradley P. Weegman Prof. Dr. Michael Garwood Prof. Dr. William C. K. Pomerantz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6540-6544
19F MRI is valuable for in vivo imaging due to the only trace amounts of fluorine in biological systems. Because of the low sensitivity of MRI however, designing new fluorochemicals remains a significant challenge for achieving sufficient 19F signal. Here, we describe a new class of high-signal, water-soluble fluorochemicals as 19F MRI imaging agents. A polyamide backbone is used for tuning the proteolytic stability to avoid retention within the body, which is a limitation of current state-of-the-art perfluorochemicals. We show that unstructured peptides containing alternating N-ϵ-trifluoroacetyllysine and lysine provide a degenerate 19F NMR signal. 19F MRI phantom images provide sufficient contrast at micromolar concentrations, showing promise for eventual clinical applications. Finally, the degenerate high signal characteristics were retained when conjugated to a large protein, indicating potential for in vivo targeting applications, including molecular imaging and cell tracking. 相似文献
10.
An NMR cell with two pieces of thin platinum (Pt) negative and positive electrodes having a thickness of 0.02 mm was designed as set in an NMR imaging probe, in order to study the shrinkage process of a hydro-poly(methacrylic acid) (PMAA) gel in real time under the application of an electric field. By using the newly designed NMR cell, the three-dimensional images of the shrinking of 1H spin density distribution of water in a PMAA gel on the application of a DC electric field were successfully observed in real time. From these results, the shrinkage process of the gel was analyzed. 相似文献
11.
Bi-Jie Bie Xiao-Rui Zhao Jia-Rui Yan Xi-Jun Ke Fan Liu Guo-Ping Yan 《Molecules (Basel, Switzerland)》2022,27(19)
Fluorescent imaging has been expanded, as a non-invasive diagnostic modality for cancers, in recent years. Fluorescent probes in the near-infrared window can provide high sensitivity, resolution, and signal-to-noise ratio, without the use of ionizing radiation. Some fluorescent compounds with low molecular weight, such as rhodamine B (RhB) and indocyanine green (ICG), have been used in fluorescent imaging to improve imaging contrast and sensitivity; however, since these probes are excreted from the body quickly, they possess significant restrictions for imaging. To find a potential solution to this, this work investigated the synthesis and properties of novel macromolecular fluorescent compounds. Herein, water-soluble dextran fluorescent compounds (SD-Dextran-RhB) were prepared by the attachment of RhB and sulfadiazine (SD) derivatives to dextran carrier. These fluorescent compounds were then characterized through IR, 1H NMR, 13C NMR, UV, GPC, and other methods. Assays of their cellular uptake and cell cytotoxicity and fluorescent imaging were also performed. Through this study, it was found that SD-Dextran-RhB is sensitive to acidic conditions and possesses low cell cytotoxicities compared to normal 293 cells and HepG2 and HeLa tumor cells. Moreover, SD-Dextran-RhB demonstrated good fluorescent imaging in HepG2 and HeLa cells. Therefore, SD-Dextran-RhB is suitable to be potentially applied as a probe in the fluorescent imaging of tumors. 相似文献
12.
The use of NMR imaging techniques for the characterization of superabsorbing polymers is explored. Spatial differences in
the cross-link densities of polyacrylate-based superabsorbing particles are investigated by parameter-selective 1H NMR imaging of samples swollen with water. Images of the transverse relaxation time and of the self-diffusion coefficient
of the absorbed water provide valuable information on the local water mobility and, thus, indirectly also on the polymer.
The time evolution of the swelling process was also studied by NMR images acquired after different swelling times. Moreover,
using magic-angle-spinning imaging, the influence of mechanical load on the swollen particle was investigated by taking advantage
of the centrifugal forces on the spinning sample. These experiments indicate the presence of two water components, one strongly
adsorbed, while the other is relatively mobile.
Received: 2 November 1999 Accepted: 17 December 1999 相似文献
13.
Several 1,2,3-triazole-linked glycoconjugates were efficiently synthesized via a Cu(I)-mediated 1,3-dipolar cycloaddition with high regiospecificity and yield (≥ 85%), providing a simple and efficient route to synthesize protected and unprotected neoglycoconjugates. Introduction of a spacer between glycosyl moieties and other compounds reduces steric hindrance, promotes yield, and expands the varieties of glycoconjugates to satisfy various needs of biological events. The structures of all the synthesized glycoconjugates were clearly confirmed by infrared(IR), 1H NMR, 13C NMR, elemental analysis (EA), or MS. 相似文献
14.
A.F. Maarten Altelaar Ioana M. Taban Liam A. McDonnell Peter D.E.M. Verhaert Robert P.J. de Lange Roger A.H. Adan Wolter J. Mooi Ron M.A. Heeren Sander R. Piersma 《International journal of mass spectrometry》2007,260(2-3):203
Matrix assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) has been used to determine peptide distributions directly from rat, mouse and human pituitary tissue sections. Since these organs are small (102–103 μm) the spatial resolution of IMS is a key issue in molecular imaging of pituitary tissue sections. Here we show that high-resolution IMS allows localization of neuropeptide distributions within different cell clusters of a single organ of a pituitary tissue section. The sample preparation protocol does not result in analyte redistribution and is therefore applicable to IMS experiments at cellular length scales. The stigmatic imaging mass spectrometer used in this study produces selected-ion-count images with pixel sizes of 500 nm and a resolving power of 4 μm, yielding superior spatial detail compared to images obtained in microprobe imaging experiments. Furthermore, we show that with imaging mass spectrometry a distinction can be made between different mammalian tissue sections based on differences in the amino acid sequence of neuropeptides with the same function. This example demonstrates the power of IMS for label-free molecular imaging at relevant biological length scales. 相似文献
15.
Sensitivity enhancement by the use of inductively coupled milli‐ and microcoils has been demonstrated in solid‐state as well as liquid‐state NMR. In this work, we discuss the practical aspects of using inductively coupled solenoid coils of different sizes in a liquid‐state NMR spectrometer. The sensitivity and resolution enhancements from these resonant coils, with sizes ranging between 3.0 and 0.75 mm i.d., are measured for 23Na single‐pulse and multidimensional imaging experiments and compared to the results obtained with the conventional liquids NMR 5.0‐mm saddle coil. Enhancements in voxel‐based sensitivity (SNR per √scans) were measured in multidimensional MR images and were found to be as large as 20.4 with the 0.75‐mm coil. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
Dr. Matteo P. Placidi Prof. Dr. Mauro Botta Dr. Ferenc K. Kálmán Dr. Gisela E. Hagberg Dr. Zsolt Baranyai Andreas Krenzer Alexandria K. Rogerson Prof. Dr. Imre Tóth Prof. Dr. Nikos K. Logothetis Priv.‐Doz. Dr. Goran Angelovski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11644-11660
A series of low molecular weight lanthanide complexes were developed that have high 1H longitudinal relaxivities (r1) and the potential to be used as dual frequency 1H and 19F MR probes. Their behavior was investigated in more detail through relaxometry, pH‐potentiometry, luminescence, and multinuclear NMR spectroscopy. Fitting of the 1H NMRD and 17O NMR profiles demonstrated a very short water residence lifetime (<10 ns) and an appreciable second sphere effect. At lower field strengths (20 MHz), two of the complexes displayed a peak in r1 (21.7 and 16.3 mM ?1 s?1) caused by an agglomeration, that can be disrupted through the addition of phosphate anions. NMR spectroscopy revealed that at least two species are present in solution interconverting through an intramolecular binding process. Two complexes provided a suitable signal in 19F NMR spectroscopy and through the selection of optimized imaging parameters, phantom images were obtained in a MRI scanner at concentrations as low as 1 mM . The developed probes could be visualized through both 1H and 19F MRI, showing their capability to function as dual frequency MRI contrast agents. 相似文献
17.
1,4‐Pentadien‐3‐one‐1,5‐bis(p‐hydroxyphenyl) (PBHP) was prepared by reacting p‐hydroxybenzaldehyde and acetone in the presence of an acid catalyst. 1,4‐Pentadiene‐3‐one‐1‐p‐hydroxyphenyl‐5‐p‐phenyl methacrylate (PHPPMA) monomer was prepared by reacting PBHP dissolved in ethyl methyl ketone (EMK) with methacryloyl chloride in the presence of triethylamine. A free‐radical solution polymerization technique was used for synthesizing homo‐ and copolymers of different feed compositions of PHPPMA and ethyl acrylate (EA) in EMK as a solvent with benzoyl peroxide as a free‐radical initiator at 70 ± 1 °C. All the polymers were characterized with IR and 1H NMR techniques. The compositions of the copolymers were determined with the 1H NMR technique. The copolymer reactivity ratios were evolved with Kelen–Tudos (EA = 1.25 and PHPPMA = 0.09) and extended Kelen–Tudos (EA = 1.30 and PHPPMA = 0.09) methods. Q (0.48) and e (1.68) values for the new monomer (PHPPMA) were calculated with the Alfrey–Price method. UV absorption spectra for poly(PHPPMA) showed two absorption bands at 302 and 315 nm. The photocrosslinking properties of the polymer samples were examined with the solvent method. Thermal analyses of the polymers were performed with the thermogravimetric‐differential thermogravimetric technique. First, the decomposition temperatures started for poly(PHPPMA), copoly(EA‐PHPPMA) (62:38), and copoly(EA‐PHPPMA) (41:59) were at 350, 410, and 417 °C, respectively. A gel permeation chromatographic method was used for determining the polymer molecular weights (weight‐average molecular weight: 2.67 × 104 and number‐average molecular weight: 1.41 × 104) and polydispersity index (1.89). The solubility of the monomer and the copolymers occurred at 30 °C with solvents having different polarities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1632–1640, 2003 相似文献
18.
The present study deals with changes in the nature of pipe material (isotactic polypropylene unpigmented, pigmented) during burst tests. In practical operation standardized burst tests are commonly used. The observed recrystallization increases proportionally to the temperature and time of storing and is effective even after 2500 h. Increasing crystallinity effects a rise of the determined Ultra Micro Hardness (UMH) of the pipe material. The application of an internal pressure in the pipe, however, increases the UMH to a remarkably higher extent than the simple influence of crystallinity. The pipes which are exposed to burst tests show creep effects of the material; these effects cause a higher hardness and increasing internal stresses of the pipe material. During the burst tests the original internal stresses are reduced by the influence of heat; on the other hand new internal stresses are introduced by the creep of the material caused by the effects of the internal pressure. The influence of recrystallization and the creep during burst tests of pipes on microscopical visible changes of the material will be shown in a following paper [18]. 相似文献
19.
Qing‐Fa Si Xiao‐Dong Fan Yu‐Yang Liu Jie Kong Sheng‐Jie Wang Wen‐Qiang Qiao 《Journal of polymer science. Part A, Polymer chemistry》2006,44(10):3261-3270
Three UV‐sensitive, hyperbranched‐poly(siloxysilane)‐based polymeric photoinitiators, bearing an alkyl phenone moiety linked to the surface of the hyperbranched polymer, were synthesized via the hydrosilylation of hyperbranched poly(siloxysilane) and modified UV‐sensitive compounds. Hyperbranched poly(siloxysilane) was prepared via the polyhydrosilylation of the AB2‐type monomer methylvinyldichlorosilane. The chemical structures of the polymeric photoinitiators were characterized with 1H, 13C, and 29Si NMR, elemental analysis, Fourier transform infrared, differential scanning calorimetry, UV spectrophotometry, and thermogravimetric analysis. The UV‐curing behaviors of the blends of the hyperbranched polymeric photoinitiators with UV‐curable epoxy acrylate (EA) resin were determined by Fourier transform infrared, and the results showed that the initiation efficiency of the polymeric photoinitiators was excellent and that the thermostability of the EA/polymeric photoinitiator curing systems was higher than that of the EA/photoinitiators. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3261–3270, 2006 相似文献
20.
Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), temperature-programmed desorption of ammonia (NH3-TPD) and ultraviolet-visible spectroscopy (UV-vis). The SEM images clearly show that all zeolite crystals possess the similar morphology with particle size of about 300 nm, the TEM images reveal that irregular intracrystal pores are randomly distributed in the whole crystal. 27Al MAS NMR spectra indicate that nearly all of the Al atoms are in tetrahedral co-ordination in ZSM-5, UV-vis spectra confirm that nearly all of titanium atoms are incorporated into the framework of TS-1. The catalytic activity of meso-ZSM-5 in acetalization of cyclohexanone and meso-TS-1 in hydroxylation of phenol was also studied. The synthesis method reported in this paper is cost-effective and environmental friendly, can be easily expended to prepare other hierarchical structured zeolites. 相似文献