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排序方式: 共有417条查询结果,搜索用时 203 毫秒
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94.
Andy Shun-Hoi CHEUNG Sammual Yu-Lut LEUNG Franky Ka-Wah HAU Vivian Wing-Wah YAM 《高等学校化学研究》2021,37(5):1079-1084
Alkynylplatinum(II) bzimpy complexes of trimethylammonium-benzylethynyl ligand have been synthesized and characterized. Complexes with long alkyl chains have been found to exhibit interesting self-assembly properties in the acetonitrile solution. The amphiphilic nature of the complexes has led to the formation of nanorods, as revealed by electron microscopy experiments. Further increasing the polarity of the solvent media has given rise to the enhancement of low-energy emission. 相似文献
95.
Francisco Riquelme Paul Northrup José Luis Ruvalcaba-Sil Vivian Stojanoff D. Peter Siddons Jesús Alvarado-Ortega 《Applied Physics A: Materials Science & Processing》2014,116(1):97-109
Chiapas amber is a natural occurring fossil resin structurally composed of long macromolecule chains with semicrystalline phases associated with both fossil and polymerization process. The most conspicuous characteristic of this fossil polymer is that it preserves ancient organic inclusions. In the present work, PIXE/RBS spectrometry (particle-induced X-ray emission/Rutherford backscattering) were combined with complementary K-edge XANES spectroscopy (X-ray absorption near-edge structure) to identify the amount of sulfur in Chiapas amber. Initially, the amber samples were examined using infrared reflected photomicrography. Amber is transparent to infrared light and so embedded plants and animals are easily visible, showing them in extraordinary detail, as if they were immersed in a water-like solution. The PIXE/RBS data show that the proportion of sulfur in amber is significantly higher than that found in recently formed resins, consistent with the biogeochemical process that transforms the resin into amber during long-term burial in geological deposits. The sulfur K-edge XANES spectra from amber confirm the sulfur abundance and reveal sulfur species in the reduced and intermediate oxidation states in amber. Almost no oxidized sulfur was found, whereas the recent resins show mostly oxidized sulfur fractions. This indicates that labile oxidized sulfur decays during fossilization and resin maturation must occur under conditions of oxygen depletion. The implications of the presence of sulfur in amber for organic preservation is also discussed here. Sulfur compounds work as a polymer additive that promotes intense resin solidification. This restricts the early oxidant-specific biodegradation of the embedded biomatter and, over geological time, provides greater stability against chemical changes. 相似文献
96.
Z. Vivian Feng Ian L. Gunsolus Tian A. Qiu Katie R. Hurley Lyle H. Nyberg Hilena Frew Kyle P. Johnson Ariane M. Vartanian Lisa M. Jacob Samuel E. Lohse Marco D. Torelli Robert J. Hamers Catherine J. Murphy Christy L. Haynes 《Chemical science》2015,6(9):5186-5196
Although nanomaterials facilitate significant technological advancement in our society, their potential impacts on the environment are yet to be fully understood. In this study, two environmentally relevant bacteria, Shewanella oneidensis and Bacillus subtilis, have been used as model organisms to elucidate the molecular interactions between these bacterial classes and Au nanoparticles (AuNPs) with well-controlled and well-characterized surface chemistries: anionic 3-mercaptopropionic acid (MPA), cationic 3-mercaptopropylamine (MPNH2), and the cationic polyelectrolyte poly(allylamine hydrochloride) (PAH). The data demonstrate that cationic, especially polyelectrolyte-wrapped AuNPs, were more toxic to both the Gram-negative and Gram-positive bacteria. The levels of toxicity observed were closely related to the percentage of cells with AuNPs associated with the cell surface as measured in situ using flow cytometry. The NP concentration-dependent binding profiles were drastically different for the two bacteria strains, suggesting the critical role of bacterial cell surface chemistry in determining nanoparticle association, and thereby, biological impact. 相似文献
97.
Vivian C. Selma Luís H. B. Cotrim José A. D. Rodrigues Suzana M. Ratusznei Marcelo Zaiat Eugenio Foresti 《Applied biochemistry and biotechnology》2010,162(8):2365-2380
The effect of organic matter and fill time on anaerobic sequencing batch reactor (5 L, 30°C, 8-h cycles, 50 rpm) efficiency
has been analyzed. Organic matter was increased by the influent concentration. Fill times investigated were in the batch mode
and fed-batch followed by batch. In the batch mode organic matter removal were 93%, 81%, and 66% for influent concentration
of 500, 1,000, and 2,000 mgCOD/L (0.6, 1.29, and 2.44 gCOD/L.d), respectively. At 3,000 mgCOD/L (3.82 gCOD/L.d) operational
stability could not be achieved. Removal efficiency was improved by increasing the fill time, and was 85% for the 1,000 mgCOD/L
condition and fill times of 2 and 4 h, and 80 and 77% for the 2,000 mgCOD/L condition and fill times of 2 and 4 h, respectively.
Hence, gradual feeding seemed to improve and to smooth the profiles of organic matter and volatile acids along the cycle with
78 to 96 NmLCH4/gCOD. 相似文献
98.
A theoretical survey of the electronic structure of Ca(2) is presented using two-electron pseudopotentials complemented by core-polarization operators on Ca atoms and multireference configuration interaction/quasidegenerate perturbation theory (MRCI/QDPT) treatment of molecular excited states. The spectroscopic constants of 70 electronic states up to 30,000?cm(-1) above the ground state are determined. This implies all Ca(2) states dissociating up to the Ca(4s(2) (1)S) + Ca(4s5p (3,1)P) dissociation limits. All spin states (singlet, triplet, and quintet) are investigated. The work emphasizes the variety of interactions implying singly valence and lowest Rydberg excited states, doubly excited states generated by atom pairs (3)P(4s4p) + (3)P(4s4p), or (3)P(4s4p) + (3)D(4s3d), 4p3d double excitations asymptotically localized on a single-atom. Zwitterionic Ca(+) + Ca(-) configurations are evidenced and shown to induce specific electronic patterns in (1)Σ(g)(+), (3)Σ(g)(+), (1)Σ(u)(+), (3)Σ(u)(+), (1)Π(g), (3)Π(g), (1)Π(u), and (3)Π(u) symmetry manifolds. They also provide insight for qualitative features (barriers) found for the lower electronic states already investigated in previous publications by other authors. 相似文献
99.
Matrab T Yassar A Viau G Chakroune N Fievet F Lacaze PC 《Journal of colloid and interface science》2006,296(1):95-101
Monodisperse ruthenium nanoparticles functionalized by electroactive oligothiophenes have been prepared and characterized. Using TEM, UV-visible and FTIR we established that the organization of these nanoparticles into nanospheres can be directly controlled via modulation of the pi-pi interaction between the organic components adsorbed on the surface. This finding also shows that the self-assembled nanoheterostructures may be switched from monodisperse nanoparticles to ordered nanospheres by tuning the pH. 相似文献
100.
An [corrected] acetamidate-bridged dinuclear platinum(ii) terpyridyl complex has been isolated in two crystal forms, a red form and a dark form, with different luminescence properties; electronic absorption, emission and (1)H NMR studies revealed the presence of a dimerization process in the solution state. 相似文献