大尺度粗糙地面的电磁散射特性

 综合考虑空间区域分割、消息传递、负载平衡及同步和边界处理等因素,给出了计算随机粗糙地面电磁散射的并行时域有限差分算法流程,并在大型高性能并行机上应用。理论分析和仿真结果表明：该算法可以快速准确地计算大尺度随机粗糙地面的电磁散射特性;通过与经典解析方法的比较,验证了该算法的正确性和实用性,在大尺度情况下拟合结果更好,更能体现地面的统计特性。     

Photosystem II activity and turnover of the D1 protein are impaired in the psbA Y112L mutant of Synechocystis PCC6803 sp.

Site-directed psbA mutants at the tyrosine Y112 position have been generated in Synechocystis PCC6803 cells. The mutation Y112F does not affect photosystem II (PSII) activity as compared with control 4 delta 1K cells. However, the Y112L mutant exhibits a photosynthetically impaired phenotype. PSII activity is not detectable in this mutant when grown at 30 mumol photons m-2 s-1, while low levels of the D1 and D2 proteins and oxygen evolution activity are present in the mutant cells grown at a low light intensity (0.5-1 mumol m-2 s-1). The recombination of the QB-/S2,3 states of PSII in the Y112L mutant cells as detected by thermoluminescence (TL) is altered. The TL signal emission maximum of these cells due to charge recombination of the S2,3/QB- occurs at 20 degrees C as compared to 35-40 degrees C for the wild-type cells, indicating a possible change in the S2,3/Yz equilibrium. The Y112L mutant cells are rapidly photoinactivated and impaired in the recovery of the PSII activity. These results suggest that replacement of the aromatic residue at position Y112 by a hydrophobic amino acid may alter the function of the donor-side activity and affects the degradation and replacement of the PSII core proteins.     

Depolarization in reentrant spin glasses: a comparison between neutron and muon probes

In the amorphous ( Fe_1-x Mn_x)₇₅ P₁₆ B_6 Al_3 alloys, muon and neutron depolarization data, combined with the results of small angle neutron scattering, magnetization and Mössbauer spectroscopy, probe the existence of three distinct magnetic transitions at T_C, T_K and T_F (T_F < _K < _C).     

Detection, characterization and identification of major constituents in Zhimu-Baihe herb-pair extract by fast high-performance liquid chromatography and time-of-flight mass spectrometry through dynamic adjustment of fragmentor voltage

This work describes a novel methodology for unequivocal identification of chemical constituents in Zhimu‐Baihe herb‐pair (ZMBHHP). Compounds were removed from ZMBHHP by ultrasonic extraction with 70% ethanol, and then analyzed by fast high‐performance liquid chromatography (HPLC) coupled with time‐of‐flight mass spectrometry (TOFMS). The accurate‐mass capability of the TOF analyzer allowed reliable confirmation of the identity of the detected compounds, normally with mass errors below 3 ppm in routine analysis. This mass accuracy was sufficient to verify the elemental compositions of the chemical constituents in ZMBHHP. With dynamic adjustment of fragmentor voltage in TOFMS, an efficient ion transmission was achieved to obtain the best sensitivity and abundant fragmentation. By accurate mass measurements for each molecular ion and subsequent fragment ions, a reliable identification and differentiation of 24 saponins, 3 xanthones, 1 anthraquinone and 2 alkaloids was described here, including four groups of isomers. It is concluded that this fast and sensitive HPLC/ESI‐TOFMS technique is powerful in qualitative analysis of complex herbal medicines in terms of sensitivity, selectivity, resolving power, time savings and lower solvent consumption. Furthermore, the data gathered in this study may be helpful for understanding the synergistic nature of this herb pair in traditional Chinese medicine (TCM) and further pharmacokinetic studies of ZMBHHP. Copyright © 2010 John Wiley & Sons, Ltd.     

Statistical modeling to promote students’ aggregate reasoning with sample and sampling

While aggregate reasoning is a core aspect of statistical reasoning, its development is a key challenge in statistics education. In this study we examine how students’ aggregate reasoning with samples and sampling (ARWSS) can emerge in the context of statistical modeling activities of real phenomena. We present a case study on the emergent ARWSS of two pairs of sixth graders (age 11–12) involved in statistical data analysis and informal inference utilizing TinkerPlots. The students’ growing understandings of various statistical concepts is described and five perceptions the students expressed are identified. We discuss the contribution of modeling to these progressions followed by conclusions and limitations of these results. While idiosyncratic, the insights contribute to the understanding of students’ aggregate reasoning with data and models, with regards to samples and sampling.     

From DNA to transistors

The rapid advance in molecular biology and nanotechnology opens up the possibility to explore the interface between biology and electronics at the single-molecule level. We focus on the organization of molecular electronic circuits. Interconnecting an immense number of molecular devices into a functional circuit and constructing a framework for integrated molecular electronics requires new concepts. A promising avenue relies on bottom-up assembly where the information for the circuit connectivity and functionality is embedded in the molecular building blocks. Biology can provide concepts and mechanisms for advancing this approach, but there is no straightforward way to apply them to electronics since biological molecules are essentially electrically insulating. Bridging the chasm between biology and electronics therefore presents great challenges. Circuit organization on the molecular scale is considered and contrasted with the levels of organization presented by the living world. The discussion then focuses on our proposal to harness DNA and molecular biology to construct the scaffold for integrated molecular electronics. DNA metallization is used to convert the DNA scaffold into a conductive one. We present the framework of sequence-specific molecular lithography based on the biological mechanism of homologous genetic recombination and carried out by the bacterial protein RecA. Molecular lithography enables us to use the information encoded in the scaffold DNA molecules for directing the construction of an electronic circuit. We show that it can lead all the way from DNA molecules to working transistors in a test-tube. Carbon nanotubes are incorporated as the active electronic components in the DNA-templated transistors. Our approach can, in principle, be applied to the fabrication of larger-scale electronic circuits. The realization of complex DNA-based circuits will, however, require new concepts and additional biological machinery allowing, for example, feedback from the electronic functionality to direct the assembly process and adaptation mechanisms.     

Stability of exponential utility maximization with respect to market perturbations

We investigate the continuity of expected exponential utility maximization with respect to perturbation of the Sharpe ratio of markets. By focusing only on continuity, we impose weaker regularity conditions than those found in the literature. Specifically, we require, in addition to the V$V$-compactness hypothesis of Larsen and ?itkovi? (2007) [13], a local bmo$bmo$ hypothesis, a condition which is essentially implicit in the setting of [13]. For markets of the form S=M+∫λd〈M〉$S=M+\int \lambda d〈M〉$, these conditions are simultaneously implied by the existence of a uniform bound on the norm of λ⋅M$\lambda \cdot M$ in a suitable bmo$bmo$ space.     

Synthetic infrared spectra

We have designed, microfabricated, and characterized a diffractive optical element that reproduces the infrared spectrum of HF from 3600 to 4300 cm(-1) . The reflection-mode diffractive optic consists of 4096 lines, each 4.5mum wide, at 16 discrete depths relative to the substrate from 0 to 1.2 mum and was fabricated upon a silicon wafer by anisotropic reactive ion-beam etching in a four-mask-level process. We envisage the use of diffractive optical elements of this type as the basis for a new class of miniaturized, remote chemical sensor systems based on correlation spectroscopy.     

The Uptake and Assembly of Alkanes within a Porous Nanocapsule in Water: New Information about Hydrophobic Confinement

In Nature, enzymes provide hydrophobic cavities and channels for sequestering small alkanes or long‐chain alkyl groups from water. Similarly, the porous metal oxide capsule [{Mo^VI₆O₂₁(H₂O)₆}₁₂{(Mo^V₂O₄)₃₀(L)₂₉(H₂O)₂}]^41? (L=propionate ligand) features distinct domains for sequestering differently sized alkanes (as in Nature) as well as internal dimensions suitable for multi‐alkane clustering. The ethyl tails of the 29 endohedrally coordinated ligands, L, form a spherical, hydrophobic “shell”, while their methyl end groups generate a hydrophobic cavity with a diameter of 11 Å at the center of the capsule. As such, C₇ to C₃ straight‐chain alkanes are tightly intercalated between the ethyl tails, giving assemblies containing 90 to 110 methyl and methylene units, whereas two or three ethane molecules reside in the central cavity of the capsule, where they are free to rotate rapidly, a phenomenon never before observed for the uptake of alkanes from water by molecular cages or containers.