Nonradiative Energy Losses and Radiation Trapping in Neodymium-Doped Phosphate Laser Glasses

Fluorescence radiation trapping and nonradiative energy losses from the Nd³⁺⁴F_3/2 state are reported for two widely used commercial phosphate laser glasses (LHG-8 and LG-770). The effects of hydroxyl-group, transition-metal (Cu, Fe, V, Co, Ni, Cr, Mn, and Pt), and rare-earth (Dy, Pr, Sm, and Ce) impurities on the ⁴F_3/2 nonradiative decay rate in these glasses are quantified. Nd concentration quenching effects are reported for doping levels ranging from about 0.5 × 10²⁰ to 8.0 × 10²⁰ ions/cm³. The results are analyzed using the Förster–Dexter theory for dipolar energy transfer. Quenching rates for transition-metal ions correlate with the magnitude of spectral overlap for Nd emission (donor) and the metal ion absorption (acceptor). The nonradiative decay rates due to hydroxyl groups follow Förster–Dexter theory except at low Nd-doping levels (≲2 × 10²⁰ ions/cm³) where the quenching rate becomes independent of the Nd concentration. The data suggest a possible correlation of OH sites with Nd ions in this doping region. The effects of radiation trapping on the fluorescence decay are reported as a function of sample size, shape, and doping level. The results agree well with the theory except for samples with small doping-length products; in these cases, multiple internal reflections from the sample surfaces enhance the trapping effect.     

淀粉基重金属捕集剂的表征及捕集效能

以天然高分子淀粉为原料,采用季铵型醚化剂、三聚磷酸钠及尿素对其多元修饰的方法,最终获得多种电荷分布的以淀粉为基础的重金属捕集剂。通过FTIR、固体核磁共振波谱、TGA、SEM及捕集效能评价研究了淀粉基捕集剂的微观结构、特性及捕集机理。结果表明:淀粉分子成功引入阳离子季铵基团、阴离子磷酸基团及非离子酰胺基团;相对于原淀粉,所获得的中间体及终产物比表面积不断增大,分子量依次增加,有利于对重金属离子进行捕集;0.06 g淀粉基捕集剂对质量浓度为30 mg/L混合溶液中Cu~(2+)、Pb~(2+)、Cd~(2+)、Ni~(2+)的去除率分别为97.93%、99.83%、99.80%、99.53%,均达到国家排放标准;其捕集吸附过程符合伪二级吸附模型,且由电性中和反应和微孔吸附联合共同控制。     

Strained Mono- and Dications. On the Structures of [(CCH2)7H]2⊕ and [(CCH3)7CH3]2⊕ Dications

The reactions of alcohol 1 with HF-SbF₅ and of alcohol 8 with FSO₃H-SbF₅ at low temperatures afforded dications [(CCH₃)₇H]^2⊕ and [(CCH₃)₇CH₃]^2⊕, respectively. Both NMR (¹H and ¹³C) data and analysis of the products, obtained upon quenching of the cations, were used to discuss the possible structures of these cations. Both ions showed a remarkable NMR behaviour, viz. an equivalency of all methylgroups on the one hand and all skeleton carbon atoms on the other hand, indicating a high symmetry or a rapid (on the NMR time scale) process. Using model compounds the weighted average ¹³C-NMR chemical shifts of reasonable structures for the ions were calculated and compared with the experimentally obtained values. The conclusion is drawn that the former reaction presumably leads to dications 34 and 36 and the latter reaction to dication 51 .     

Trapping levels in pulse-counting synthetic diamond detectors

Type Ib synthetic diamonds were used as pulse-counting radiation detectors. Special ion-implanted contacts to the diamond were used. These contacts were shown to suppress the development of space charge within the diamond, and to cause no significant voltage drop across the contacts. An initial large γ-ray pre-irradiation dose markedly improved the pulse counting response of the diamond. It is suggested that this improvement is due to relevent and involved traps being filled to saturation by charge carriers whereas the same traps in an under-populated state actively inhibit the charge collection for pulse formation. The traps are depopulated by exposure to ambient light and, using this depopulation effect, the effective energy level of these involved traps was measured to be 2.2 eV. Shallow trapping levels are postulated and are believed to be responsible for the trapping of the carriers which gives rise to space charge effects.     

Trapping two-particle arrays in a double-ring electrodynamic balance

A new technique has been developed to explore the characteristics and dynamics of the electrodynamic balance (EDB). It is demonstrated that by trapping a pair of microparticles, the electric field of and EDB can be characterized and particle stability can be investigated. The electric field in the neighborhood of the null-point was examined by comparing the oscillatory motion of the two-particle system with a theoretical analysis. In addition, the relevant balance constants were evaluated by five methods: (i) determination of the stabilization strength constant, C₁, using measurements on two-particle arrays, (ii) determination of the levitation strength constant, C₀, using measurements on single particles of known mass and charge, (iii) computation of C₁ and C₀ by solving the three-dimensional Laplace equation for the non-axisymmetric electrode system, (iv) computation of C₀ using a ring charge simulation technique, and (v) determination of the ratio C₁/C₀ by measurements of the marginal stability limit. The results of the different methods are compared and shown to be consistent.     

Observation of Vacancies by Positron Trapping in Cerium-Doped Zirconolites

Positron annihilation lifetime measurements on cerium-doped zirconolites have given strong indications of positron trapping in samples that have previously been deduced to contain cation vacancies, mainly from X-ray absorption spectroscopy, thermogravimetry, and microanalysis. The increases in lifetime of the majority lifetime component are ∼20% for samples deduced to contain a few percent of vacant cation sites. Lanthanum-doped SrTiO₃ samples, in which it is generally agreed that A-site vacancies are produced via the lanthanum doping, have been used as a model system and similar increases in lifetime have been observed for samples that contain more than ∼0.1 formula units of lanthanum.     

Trapping Iron Oxide into Hollow Gold Nanoparticles

Synthesis of the core/shell-structured Fe₃O₄/Au nanoparticles by trapping Fe₃O₄ inside hollow Au nanoparticles is described. The produced composite nanoparticles are strongly magnetic with their surface plasmon resonance peaks in the near infrared region (wavelength from 700 to 800 nm), combining desirable magnetic and plasmonic properties into one nanoparticle. They are particularly suitable for in vivo diagnostic and therapeutic applications. The intact Au surface provides convenient anchorage sites for attachment of targeting molecules, and the particles can be activated by both near infrared lights and magnetic fields. As more and more hollow nanoparticles become available, this synthetic method would find general applications in the fabrication of core–shell multifunctional nanostructures.     

The Trapping Concept in Nonlinear Viscoelasticity of Amorphous Glassy Polymers

Abstract

Nonlinear stress - strain relations are derived for the viscoelastic behavior of glassy polymers. An amorphous medium is treated as an ensemble of cooperatively rearranging regions (flow units). Any unit is thought of as a point in the phase space which hops (being thermally activated) to higher energy levels in its potential well on the energy landscape. The viscoelastic behavior of a polymer is modeled as a sequence of rearrangement events occurring at random times when relaxing regions reach (in hops) some liquid-like level. We assume that external loads affect the position of the liquid-like state with respect to the energy landscape, and the descent of the reference energy level is proportional to the average mechanical energy of a flow unit. This hypothesis is verified by comparison of observations for polycarbonate in tensile relaxation tests with results of numerical simulation. Fair agreement is demonstrated between experimental data and their predictions.     

Probability of Trapping Solid Particles during Zone Melting

Abstract

The probability P of trapping of glass beads was measured for tilt rotating zone melting of camphor. P increased with increasing zone travel rate, increasing tilt angle, decreasing tube rotation, and increasing mass of beads. P also decreased dramatically with distance down the tube. This is attributed to increasing impurity content as the zone moves down the tube and by the changing shape of the freezing interface due to the diminished content of glass beads. Trapping was predominantly by periodic bands, indicating one or more catastrophic trapping mechanisms.     

化工业减排和CO_2捕集的开发进展

介绍了世界化工行业减排和CO2捕集的开发进展情况。     

Trapping characteristics of cesium in off-gas stream using fly ash filter

The cesium trapping characteristics with changing reaction temperature, carrier gas and gas velocity by the fly ash filter were analyzed. The SEM (Scanning electron microscope) on the pore structure of the fly ash filter showed that pores up to 0.1 mm in diameter were widely interconnected with each other throughout the whole structure of the filter. According to the XRD (X-ray diffraction) analysis for the cesium compound trapped on the fly ash filter, the thermally stable pollucite phase was formed. The cesium trapping quantity of the fly ash filter was increased with increasing reaction temperature, whereas it was decreased with increasing gas velocity. SEM showed that the fly ash filter after trapping gaseous cesium had mullite phase of needle-like crystals and pollucite phase of bulky crystals with rough surface. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Influence of Sintering Temperature on Intrinsic Trapping in Zinc Oxide-Based Varistors

The ac electrical data of the ZnO-Bi₂O₃ varistor system, in the frequency range 5 Hz to 13 MHz, when analyzed in the complex capacitance ( C *) plane, yields a distinct depressed semicircular relaxation having an average time constant on the order of 10⁻⁶ s. This trapping is attributed to the possible formation of ionized intrinsic/native defects. The decrease in the depression angle and average relaxation time, monitored as a function of the increasing sintering temperature (≥1100°C), indicated an improvement in the degree of uniformity in the loss-conductance and rapidity of response of the intrinsic trapping. The dependence of the ac parameters related to this trapping response obtained from the C * plane on the sintering temperature has been presented.     

Trapping of protonated phenols (ethers) by aromatics in superacids

Condensation of phenols and their methyl ethers with aromatics is easily carried out in HF–SbF₅ or in the presence of aluminum halides (AlCl₃ or AlBr₃). The postulated mechanism implies trapping of the diprotonated phenolic moiety by aromatics (benzene, naphthalene, tetrahydroquinoline) or through an intramolecular process. This revised version was published online in June 2006 with corrections to the Cover Date.     

Statistical Problems Encountered in Trapping Studies of Scolytids and Associated Insects

Traps baited with semiochemicals are often used to investigate the chemical ecology of scolytids and associated insects. One statistical problem frequently encountered in these studies are treatments that catch no insects and, thus, have zero mean and variance, such as blank or control traps. A second problem is the use of multiple comparison procedures that do not control the experimentwise error rate. We conducted a literature survey to determine the frequency of these two statistical problems in Journal of Chemical Ecology for 1990-2002. Simulations were then used to examine the effects of these problems on the validity of multiple comparison procedures. Our results indicate that both statistical problems are common in the literature, and when combined can significantly inflate both the experimentwise and per comparison error rate for multiple comparison procedures. A possible solution to this problem is presented that involves confidence intervals for the treatment means. Options to increase the statistical power of trapping studies are also discussed.     

稀土电子俘获光存储材料研究进展

电子俘获光存储技术是一种新型的存储技术,它突破了现有的光存储介质的存储机制,可实现大密度稳定可重复擦写存储。详细介绍了稀土电子俘获材料类型、光存储机制、应用前景,并展望了它的发展趋势。     

Trapping of Aromatic Compounds by Adsorption on Hydrophobic Sorbents

Abstract

Trapping by adsorption on hydrophobic porous polymers was the selected method for removing aromatic compounds from aqueous diluted medium. The study was done with four aromatic compounds which are often found in foods and which play a role in organoleptic qualities at low concentrations: ethyl acetate, 2,5-dimethylpyrazine, 1-octen 3-ol, and-γ-decalactone. Several sorbents were tested: activated carbon and three porous polystyren-type polymers (Porapak Q, Chromosorb 105, and Amberlite XAD-4). Kinetic and equilibrium sorptions were investigated. The adsorption isotherms were determined for the four aromatic and all the adsorbents, and equilibrium data were correlated with a Freundlich or a Langmuir-type of isotherm equation. Kinetic experimental results were simulated for 1-octen 3-ol using an internal-external mass transfer resistance model. Good agreement was observed for the diffusion coefficient in the sorbent in the range of 10^?8cm^2.s^?1.     

Anti-Oncogenic gem-Dihydroperoxides Induce Apoptosis in Cancer Cells by Trapping Reactive Oxygen Species

Organic gem-dihydroperoxides (DHPs) and their derived peroxides have attracted a great deal of attention as potential anti-cancer agents. However, the precise mechanism of their inhibitory effect on tumors is unknown. To determine the mechanism of the inhibitory effects of DHPs, we examined the effects of DHPs on leukemia K562 cells. As a result, certain DHPs used in this study exhibited growth-inhibitory activity according to a clear structure-activity relationship. The most potent DHP, 12AC3O, induced apoptosis in K562 cells, but not in peripheral blood monocytes (PBMCs) or fibroblast cells. 12AC3O induced apoptosis through the intrinsic mitochondrial pathway and thereafter through the extrinsic pathway. The activity of the former pathway was partly attenuated by a JNK inhibitor. Interestingly, 12AC3O induced apoptosis by trapping a large amount of ROS, leading to an extremely lower intracellular ROS level compared with that in the cells in the steady-state condition. These results suggest that an appropriate level of intracellular ROS was necessary for the maintenance of cancer cell growth. DHPs may have a potential to be a novel anti-cancer agent with minimum adverse effects on normal cells.     

Trapping of the non-wetting phase in an interacting triangular tube bundle model

An interacting triangular tube bundle model is developed using capillaries of equilateral triangle cross sections. In addition to pressure equilibration among the capillaries, the non-circular tubes allow the wetting phase to reside in the corners and flow continuously in the entire model. An interacting-serial type model is constructed with step changes of tube size along the model, while the total cross-section of the model is kept constant. This model includes trapping of oil which is absent in traditional tube bundle models. Trapping of non-wetting phase in the model in imbibition processes is simulated. The relationship between the residual oil saturation and the complete capillary number CA is investigated. The simulation results obtained by this model are consistent with the results reported in literature of both experimental studies, using actual porous media, and simulations in pore-scale network models. The effects of the tube size, tube size distribution and viscosity ratio on the magnitude of entrapment are also studied using this tube bundle model.     

Simulations of Trapping of Diesel and Gasoline Particulate Matter in Flow-through Devices

Eulerian–Lagrangian CFD modeling has been used to track eight types of typical diesel and gasoline soot particles through a flow-through substrate with protrusions. It is shown that there exists a minimum trapping efficiency for medium-sized soot particles (d _p  ≈ 150 nm). Small and large particles are trapped by different mechanisms, and thus appear in different patterns on the substrate walls.