Optical Properties of Zinc-Blende InGaN/GaN Quantum Well Structures and Comparison with Experiment

Optical properties of zinc-blende InGaN/GaN Q W structures are investigated using the multiband effective-mass theory. The transition wavelength values at 300 K ranged from 440 to 570nm in the investigated range of the In composition and the well width. The theoretical wavelengths show reasonable agreement with the experimental results. The optical gain decreases with the increasing well width. This is mainly due to the reduction in the quasi-Fermi-level separation because the optical matrix element increases with the well width.     

Spectral Analysis of Social Networks to Identify Periodicity

Two key problems in the study of longitudinal networks are determining when to chunk continuous time data into discrete time periods for network analysis and identifying periodicity in the data. In addition, statistical process control applied to longitudinal social network measures can be biased by the effects of relational dependence and periodicity in the data. Thus, the detection of change is often obscured by random noise. Fourier analysis is used to determine statistically significant periodic frequencies in longitudinal network data. Two approaches are then offered: using significant periods as a basis to chunk data for longitudinal network analysis or using the significant periods to filter the longitudinal data. E-mail communication collected at the United States Military Academy is examined.     

Basis set limit binding energies of hydrogen bonded clusters

The utility of the recently developed extrapolation method to estimate the binding energies of weakly bound clusters at the basis set limit exploiting the similar basis set convergence behaviour of correlation energies of the monomer and cluster in correlated calculations (J. chem. Phys., 116, 5389 (2002)) was tested for small to medium (HF)_n and (H₂O)_n (n = 2–5) clusters using various correlation consistent cc-pVXZ (X= D,T,Q,5) basis sets containing different numbers of diffuse functions and 6–31G type basis sets at the MP2 and CCSD(T) level for which accurate basis set limits are available for comparison. It is shown that the basis set limit binding energies estimated by this extrapolation method with modest size of basis sets (cc-pVDZ/cc-pVTZ or 6–3 1 G(d,p)/6-3 IG(2df,2pd)) are much closer to the exact basis set limits than the estimates by commonly used X ^?3 extrapolation or counterpoise corrected binding energies, signifying the importance of this extrapolation method for the study of large weakly bound clusters. It is also shown that the inclusion of appropriate diffuse functions in the basis sets can significantly improve the accuracy of the estimated basis set limits by this extrapolation method. For (HF)_n clusters the MP2 and CCSD(T) basis set limits estimated by this extrapolation method with aug-cc-pVDZ and aug-cc-pVTZ basis sets are 18.4 (18.5) and 18.9 (18.9) for the dimer, 61.8 (62) and 63.2 (63) for the trimer, 113.5 and 114.7 (116) for the tetramer, and 155.2 and 156.3 (158) for the pentamer, respectively, with the values in parentheses representing the apparent basis set limits, with the numbers in units of kJ mol^?1. The corresponding results for (H₂O)_n clusters are 20.5 (20.5) and 20.6 (20.7) for (H₂O)₂, and 60.5 (61) and 60.1 (60) for (H₂O)₃, respectively.     

Periodic solutions of Wick-type stochastic Korteweg–de Vries equations

Nonlinear stochastic partial differential equations have a wide range of applications in science and engineering. Finding exact solutions of the Wick-type stochastic equation will be helpful in the theories and numerical studies of such equations. In this paper, Kudrayshov method together with Hermite transform is implemented to obtain exact solutions of Wick-type stochastic Korteweg–de Vries equation. Further, graphical illustrations in two- and three-dimensional plots of the obtained solutions depending on time and space are also given with white noise functionals.     

有机小分子发光材料与聚合物发光材料在大气存放条件下的稳定性对比研究

分别采用紫外光电子能谱（UPS）、X光电子能谱（XPS）、原子力显微镜（AFM）、以及光致发光光谱（PL）等方法对在大气存放条件下的8－羟基喹啉铝（Alq)薄膜和聚（9,9－二辛烷基芴）（PFO）薄膜的电子结构、表面形 及发光特性进行了对比。研究结果表明,PFO的电子结构、表面形貌以及发光特性受外界气氛影响极小,是一种非常稳定的聚合物发光材料。这为聚合物发光器件的稳定性提供了有利的条件。     

Prolongation Approach to the Liouville Equation and Its Algebraic Structures

The Riccati type equation, the Biicklund transformation and the Lax pair of the Liouville equation are obtained by using the prolongation theory. It is shown that the prolongation structures generate the SL(2,R) Lie algebra.     

The Properties of Surface Polaron in the Semi-Infinite Polar Crystal

The effective Hamiltonian and the renormalized mass of surface polaron, where the electron is strongly coupled with the surface optical (SO) phonons but weakly or intermediately coupled with the bulk longit udinal-optical (LO) phonons, were first reviewed. The self-energy and the renormalized mass of the polaron for the polar crystals of potassium iodide, silver chloride and silver bromide are evaluated as a function of the depth Gom the crystal surface. Results of our calculation indicate that the effect of the electron-SO phonon interaction is dominant only within a very small layer from the crystal surface. Its justification awaits further experimental results.     

Regioselective Formation of Enediynes via Intramolecular Trapping of Allylic Cations

Enediynes are a novel class of naturally occurring antitumor antibiotics capable of causing DNA strand cleavage by hydrogen atom abstraction from the deoxyribose backbone. During the past decade, numerous synthetic methods have been developed to synthesize the naturally occurring and the "designed" enediynes for biomedical studies. Recently, we have succeeded in assembling the cis-enediynes 2 by a novel and high-yielding allylic rearrangement under mild reaction conditions (Eq 1).^1-3 This methodology has been used to synthesize a 10-membered ring enediyne³ which exhibits DNA cleavage activity.     

Preliminary Study on Destruction of Freon 12 by Inductively Coupled Plasma——Development of ICP Technology for Waste Destruction

ＰｒｅｌｉｍｉｎａｒｙＳｔｕｄｙｏｎＤｅｓｔｒｕｃｔｉｏｎｏｆＦｒｅｏｎ１２ｂｙＩｎｄｕｃｔｉｖｅｌｙＣｏｕｐｌｅｄＰｌａｓｍａ——ＤｅｖｅｌｏｐｍｅｎｔｏｆＩＣＰＴｅｃｈｎｏｌｏｇｙｆｏｒＷａｓｔｅＤｅｓｔｒｕｃｔｉｏｎＣＨＥＮＤｅｎｇ－ｙｕｎａｎ...     

Quercetin enhances vitamin D2 stability and mitigate the degradation influenced by elevated temperature and pH value

Vitamin D₂ (vit. D₂) is a nutraceutical essentially needed for good health. However, it is susceptible to oxygen and high temperature. The use of natural products such as bioflavonoids possessing anti-degradative effect of vit. D₂ degradation has not been described before. A combinational effect of vit. D₂ with quercetin showed a positive effect and inhibited vit. D₂ degradation when exposed to high temperature (50 ℃ and 75 ℃) at different time points. The results obtained revealed vit. D₂ degradation was drastically increased with longer incubation under thermal treatment. However, quercetin and vit. D₂ groups were able to significantly inhibit the degradation of vit. D₂ and stabilize it, evaluated through the retention percentage. We also exposed vit. D₂ at solutions with different pH values (1, 4, 5, 7, 10). Quercetin exerted vit. D₂ anti-degradation at different pH values as well as under thermal pressure at different time points. Conclusively, quercetin can be an effective way to reduce temperature and pH induced degradation of vit. D₂.