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71.
Koichi Itoh Takeji Takui 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(2):29
This review paper deals with an overview of molecule-based magnetism as a rapidly developing interdisciplinary field, topological symmetry rule as the first principle of spin alignment in organic open-shell systems in the ground state, the proposal of organic through-bond 1D and 2D ferro- and superparamagnets and the detection of the first organic high-spin molecule, m-phenylenebis(phenylmethylene) in the quintet ground state (S = 2), followed by extended organic high-spin systems with π-conjugation such as aromatic hydrocarbons having S = 3, 4, 5. The paper also describes a theoretical approach to the understanding of electronic spin structures of organic high-spin molecules by invoking both Heisenberg and Hubbard model Hamiltonians, weakly interacting intramolecular high-spin systems from both experimental and theoretical sides, the spin density distribution of the first organic high-spin molecule in terms of electron- nuclear multiple resonance spectroscopy and the detection and characterization of ionic high-spin hydrocarbons, emphasizing the establishment of high spin chemistry underlying organic molecular magnetism. 相似文献
72.
首次实现了LK泵浦Nd∶BGO固体激光器的1.064μm的激光输出,泵浦阈值功率为25mW,在连续运转状态下得到最大为40mW的TEM00模输出,光-光效率为13.3%,根据法拉第磁光效庆理论,了LD泵浦Nd∶BGO自调Q激光器的各种参数,并研制成该激光器,在该器件中,作为损耗调制元件的磁光调制器就是绕有线圈的Nd∶BGO晶体本身,实验在重复率为1KHz的条件下得到了FWHM为100ns的稳定脉冲 相似文献
73.
《Journal of separation science》2003,26(5):402-408
When nitrated polynuclear aromatic hydrocarbons (NPAH) were recognised as long‐term toxic compounds and were also identified in several anthropogenic emissions and among the by‐products of photochemical smog they became objects of investigation in ambient air in both polluted and clean environments. In Italy the first investigations focussing on atmospheric NPAH were performed in the early eighties and encompassed both the canyon streets and dwelling areas of Rome. Because NPAH were indicated as markers of vehicle emission, new investigations were performed in other cities and also in rural and (nominally) unpolluted locations. In general, the first measurements of NPAH were episodic and could not be assumed to be strictly representative of the sites investigated. In contrast, nowadays consistent data bases on NPAH have been built up and are discussed in the technical literature, so that both neat concentrations and the yearly timed variation of the most important NPAH congeners have been measured in Italian air. Although concentrations of NPAH in air are usually much lower than those of PAH, owing to their very high potency in inducing mutations and tumours NPAH are regarded as having an important health impact on populations living in Italian urban areas. In this regard the genotoxicity of atmospheric aerosols is partly associated with nitrofluoranthenes and nitropyrenes whereas nitronaphthalenes and methylnitronaphthalenes seem to contribute to that of the gaseous organic fraction. Several civic and regional administrations are introducing control of atmospheric NPAH among ways of improving air quality in cities. 相似文献
74.
Biological transformation of volatile organic compounds is one of the key factors that influence contaminant-plume evolution
and thus natural attenuation. In this study we investigate the effect of biological transformation on the transport of contaminants
in the aqueous and gaseous phases. The analysis includes the study of the effect of density-driven advection of contaminants
in the gaseous phase on multiphase and multispecies flow, fate and transport modeling in the subsurface. Trichloroethylene
(TCE) and its two byproducts, dichloroethylene and vinyl chloride, are analyzed as the target contaminants. Our results indicate
that density-driven advection of the gaseous phase, which is initiated by evaporation of TCE as a nonaqueous phase liquid,
increases the downward and also the lateral migration of TCE within the unsaturated zone. This process also influences the
location of high-concentration zones of the byproducts of TCE in the unsaturated and the saturated zones. Biotransformation
of TCE contributes to the reduction of dissolved TCE plume development as expected. The daughter byproducts, which are introduced
into the subsurface system, show distinct transport patterns as they are affected by their independent degradation kinetics
and density-driven advection. These observations, which are based on our simulation results for biotransformation and transport
of TCE and its byproducts, are useful in evaluating the natural attenuation processes, its potential health hazards and also
the evaluation of potential plume development at contaminated sites. 相似文献
75.
Alex M. Green David G. Gevaux Christine Roberts Chris C. Phillips 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):531
In this paper we outline the use of resonant-cavity enhancement for increasing the exterior coupling efficiency of photodetectors and light-emitting diodes (LEDs) in the mid-infrared (MIR) spectral region. This method is potentially very important in the MIR because encapsulation is not presently feasible due to the lack of suitable materials. Among other potential applications, resonant-cavity-enhanced (RCE) photodetectors and LEDs could be particularly suitable for greenhouse gas detection because of their ‘pre-tunable’ spectrally narrowed resonantly enhanced peaks. We also present the optical characterization of an InAs RCE photodetector aimed at the detection of methane gas (λ≈3.3 μm), and an InAs/InAs0.91Sb0.09 resonant-cavity LED (RCLED) aimed at carbon dioxide gas (λ≈4.2 μm). The high peak responsivity of the RCE photodetector was 34.7 A/W at λ=3.14 μm, and the RCLED peaked at λ=3.96 μm. These are among the longest operating wavelengths for III–V RCE photodetectors and RCLEDs reported in the literature. 相似文献
76.
Investigation on ultrafast thrid—order optical nonlinearity of metal(dmit)2/mnt)2 Charge transfer complexes
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We have investigated the transient third-order optical nonlinearity of the solutions of Metal(dmit)2/(mnt)2 salts in acetone by employing femtosecond optical Kerr gate measurement at 830nm wavelength.An order of enhancement on the second-order hyperppolarizability is found for the above salts with central atoms of Cu and Ni.We have suggested an explanation for the enhancement based on the extension of electronic conjugation by the entring Cu or Ni atom. 相似文献
77.
78.
79.
The stability of regioregular poly(3-hexylthiophene 2,5-diyl) (P3HT) thin films sandwiched between indium tin oxide (ITO)
and aluminium (Al) electrodes have been investigated under normal environmental conditions (25°C and RH∼45–50%). Electrical
and optical properties of ITO/P3HT/Al devices have been studied over a period of 30 days. Mobility μ of the order of 10−4 cm2/V-s has been obtained from the V
2 law in the as-deposited P3HT films. Scanning electron microscopy (SEM) investigations show blistering of Al contacts in devices
with a poly(3,4-ethylenedioxythiophene) (PEDOT) interlayer on application of voltage whereas no blistering is seen in devices
without PEDOT. The results have been explained in terms of trap generation and propagation and the moisture-absorbing nature
of PEDOT.
相似文献
80.