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561.
Young Han Lee Daekeon Lim Eunju Kim Sungjun Kim Ho-Taek Song Jin-Suck Suh 《Magnetic resonance imaging》2014
Background and Purpose
Fluid-sensitive MR imaging in postoperative evaluation is important, however, metallic artifacts is inevitable. The purpose is to investigate the feasibility of fat-saturated slice encoding for metal artifact correction (SEMAC)-corrected T2-weighted magnetic resonance (MR) at 3T in patients with spinal prostheses.Methods
Following institutional review board approval, 27 SEMAC-encoded spinal MRs between September 2012 and October 2013 in patients with spinal metallic prostheses were analyzed. The MR images were scanned on a 3T MR system including SEMAC-corrected and uncorrected fast spin echo (FSE) T2-weighted MR images with fat-saturation. Two musculoskeletal radiologists compared the image sets and qualitatively analyzed the images using a five-point scale in terms of artifact reduction around the prosthesis, visualization of the prosthesis and pedicle, and intervertebral neural foramina. Quantitative assessments were performed by calculating the ratio of signal intensity from the fixated vertebra and that from upper level vertebra. For statistical analyses, paired t-test was used.Results
Fat-saturated SEMAC-corrected T2-weighted MR images enabled significantly improved metallic artifact reduction (P < 0.05). Quantitative evaluation of the signal intensity ratio of screw-fixated vertebra and upper level vertebra showed a significantly lower ratio on fat-saturated SEMAC images (P < 0.05), however, the high signal intensity of signal pile-up could be not completely corrected.Conclusion
SEMAC correction in fat-suppressed T2-weighted MR images can overcome the signal loss of metallic artifacts and provide improved delineation of the pedicle screw and peri-prosthetic region. Signal pile-up, however, could not be corrected completely, therefore readers should be cautious in the evaluation of marrow around the prosthesis. 相似文献562.
Xi Wu Prof. Wenlei Zhang Dr. Jun Li Prof. Quanjun Xiang Prof. Zhongyi Liu Prof. Bin Liu 《Angewandte Chemie (International ed. in English)》2023,62(6):e202213124
We report an oxygen vacancy (Vo)-rich metallic MoO2−x nano-sea-urchin with partially occupied band, which exhibits super CO2 (even directly from the air) photoreduction performance under UV, visible and near-infrared (NIR) light illumination. The Vo-rich MoO2−x nano-sea-urchin displays a CH4 evolution rate of 12.2 and 5.8 μmol gcatalyst−1 h−1 under full spectrum and NIR light illumination in concentrated CO2, which is ca. 7- and 10-fold higher than the Vo-poor MoO2−x, respectively. More interestingly, the as-developed Vo-rich MoO2−x nano-sea-urchin can even reduce CO2 directly from the air with a CO evolution rate of 6.5 μmol gcatalyst−1 h−1 under NIR light illumination. Experiments together with theoretical calculations demonstrate that the oxygen vacancy in MoO2−x can facilitate CO2 adsorption/activation to generate *COOH as well as the subsequent protonation of *CO towards the formation of CH4 because of the formation of a highly stable Mo−C−O−Mo intermediate. 相似文献
563.
Synthesis and characterization of Fe(II)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)] block copolymers
In this work,a new type of block polymers,polystyrene-b-poly[(N-isopropyl acrylamide)-co-(vinyl benzyl chloride)](PS-b-P(NIPAM-co-VBC)),was prepared via reversible addition fragmentation transfer polymerization,then pentacyano(4-(dimethylamino pyridine))ferrate(Fe-DMAP) was attached to VBC units through a quaternization process.The Fe(Ⅱ)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)]block copolymers were characterized by ~1H-NMR,FT-IR and TGA.The self-assembly behavior of the block copolymers was also investigated and the micelle morphology was characterized by TEM.It was found that the PS-b-P(NIPAM-co-VBC) block polymer and Fe-coordinated block copolymer could both form spherical micelles in DMF/MeOH mixed solvent. 相似文献
564.
A variety of silica‐based solid phases, whose surfaces are functionalized with ligands containing sulfur and nitrogen elements, are used as self‐supporting adsorbents for environmental remediation evaluation and potential separation application. Each adsorbent is tested for its ability to scavenge five metallic ions: Hg2+, Cu2+, Cd2+, Mn2+, Pb2+, and two organometallic ions: ethylmercury and phenylmercury, from independent homoionic solutions at both neutral and acidic pH values. The results indicate that the percentage of these ions scavenged by a given adsorbent varies, and is found to be highly related to the structural environment in the vicinity of the sulfur and nitrogen elements on the ligand. It is believed that the scavenging of metallic ions is a result of the complexation formation between the metallic ions and the ligands containing sulfur and nitrogen elements, and is not due to the irreversible association chemistry with the sulfur or nitrogen element itself. In the case of organometallic ions, a π‐π interaction is thought to be involved in the adsorption with ligands containing an aromatic moiety in addition to the aforementioned forces. The time needed to reach the maximum percent of adsorption decreases as the amount of adsorbent increases. The longer the adsorption time, the higher percent of ion is removed. Other factors, such as the temperature and the acidity in the liquid phase of the matrix affect the percentage of ions scavenged as well. 相似文献
565.
The correlations between the pressure sensitivity and the fragility/glass transition temperature have been addressed in various bulk metallic glasses in the present work. The results demonstrate that the pressure sensitivity of bulk metallic glasses is closely related to both the fragility index (m) and the glass transition temperature (Tg). The physical origin of the correlations has been discussed from their disordered structure, which is determined by the glass transition behavior and the glass transition temperature. 相似文献
566.
Various 2-aryl-1-(4-methoxyphenyl)-5-(5-tricyanoethenyl-2-thienyl)pyrroles (3) were synthesized. When the 2-aryl group of 3 is phenyl, 4-tolyl, and 4-methoxyphenyl, organic crystals with greenish yellow metallic luster are formed. In contrast, a 2-(4-fluorophenyl) derivative of 3 gives gold-like lustrous crystals. The relation of their crystal structures with the appearance of metallic color is mentioned. 相似文献
567.
On the treatment of 1-aryl-2-(2-furyl)-5-(2-thienyl)pyrroles with tetracyanoethylene, 1-aryl-2-(2-thienyl)-5-(5-tricyanoethenyl-2-furyl)pyrroles were produced. These compounds formed crystals with greenish metallic luster. In their solid-state UV-vis-NIR diffuse reflection-absorption spectra, absorption band corresponding to metallic reflection spreads in the range of 550-900 nm. Furthermore, strong absorption appeared below 520-540 nm. This absorption results in the appearance of green color. Single-crystal X-ray crystallographic analysis revealed the crystal structure of 1-(4-methoxyphenyl)-2-(2-thienyl)-5-(5-tricyanoethenyl-2-furyl)pyrrole (2c). The distinct features of the crystal structure are as follows: (1) the thiophene-pyrrole-furan-tricyanoethenyl π-system is approximately flat; (2) the conformational relation between the pyrrole ring and the furan ring is anti, that is, these rings are pointing in opposite directions and the dihedral angle of N-C-C-O=180°; (3) as a result, the tricyanoethenyl group is far from the 4-methoxyphenyl group; (4) the molecules of 2c are arranged in a ribbon structure; (5) the ribbons are assembled side-by-side to form a terraced layer; (6) the layers stack so that the π-orbitals of 2c become close to each other. 相似文献
568.
569.
The structural transitions of Ti during two different quenching processes (Q1: 7.5×1011 K/s, Q2: 2.0×1014 K/s) were studied using molecular dynamics simulations. The calculated pair-correlation function agrees acceptably with available experimental data. This work gives the structural properties, including the variations with temperature of pair-correlation function, bond-angle distribution function, bond pairs and Voronoi indices, in both rapid quenching processes. Our results indicated that the liquid Ti transformed to hcp phase at the temperature about of 400 K under the quenching condition Q1 while the liquid Ti was frozen into a glass state at the temperature about of 800 K under the quenching condition Q2. 相似文献
570.
The temperature dependent structure of Ni81P19 metallic glasses, rapidly quenched from melts which have undergone different heat treatments, has been investigated by small angle neutron scattering and neutron diffraction. All samples contain in the as-quenched state particles or clusters of a very wide range of sizes. These are amorphous regions of different compositions in a large composition range and/or crystallites of another Ni composition than the matrix, such as Ni3P, Ni5P2 or Ni12P5, or even “voids”. The results can be interpreted within the concept of a heterogeneous structure existing in eutectic melts in a certain temperature range. Comparison is made with results from the literature on samples from the same ribbons investigated by calorimetry as well as by fractography and Weibull analysis of mechanical properties. 相似文献