Two new pyrrolizidine alkaloids from Senecio nemorensis

Two new compounds, including petasinoside A and chloridate-[N-chloromethyl-hectorine], were isolated from Senecio nemorensis. The structures of these compounds were elucidated by spectroscopic methods including 1D and 2D NMR experiments.     

DNA Polyplexes Formed Using PEGylated Biodegradable Hyperbranched Polymers

A novel PEGylated biodegradable hyperbranched PEG‐b‐PDMAEMA has been synthesized. The low toxicity, small molecular weight PDMAEMA chains were crosslinked using a biodegradable disulfide‐based dimethacrylate (DSDMA) agent to yield higher molecular weight hyperbranched polymers. PEG chains were linked onto the polymer surface, masking the positive charge (as shown by Zeta potential measurements) and reducing the toxicity of the polymer. The hyperbranched structures were also cleaved under reducing conditions and analyzed, confirming the expected component structures. The hyperbranched polymer was mixed with DNA and efficient binding was shown to occur through electrostatic interactions. The hyperbranched structures could be reduced easily, generating lower toxicity oligomer chains.

     

Local dimming algorithm and color gamut calibration for RGB LED backlight LCD display

A 32 in RGB LED backlight unit is developed. A local dimming algorithm is designed for the backlight, and grid-noise artifacts in the LC driving signal are successfully removed with consideration of the backlight distribution to provide identical intensity from each LED block. The 32 in RGB LED backlight LCD display has achieved a static display contrast of over 20000:1 and an average power reduction of 30%. We have also obtained the color gamut transformation matrix for transferring a cold cathode fluorescent lamp BLU LCD display gamut system to our RGB LED BLU LCD display gamut system, and extended the color saturation by suppositional color expansion method. As a result, the color has been accurately reproduced in RGB LED BLU LCD display with more richness and more saturation.     

Improvement of <Emphasis Type="Italic">n</Emphasis>-ZnO/<Emphasis Type="Italic">p</Emphasis>-Si photodiodes by embedding of silver nanoparticles

The photo-current of n-ZnO/p-Si heterojunction photodiodes was improved by embedding Ag nanoparticles in the interface (ZnO/nano-P_Ag/p-Si), and the ratio between photo- and dark-current increased by about three orders more than that of a n-ZnO/p-Si specimen. The improvement in the photo-current resulted from the light scattering of embedded Ag nanoparticles. The I–V curve of n-ZnO/p-Si degraded after thermal treatment (A-ZnO/p-Si) because the silicon robbed the oxygen from ZnO to form amorphous silicon dioxide and left an oxygen vacancy. Notably, the properties of ZnO/nano-P_Ag/p-Si were better in the time-dependent photoresponse under 10 V bias. Ag nanoparticles (15–20 nm) scattered the UV light randomly and increased the probability for the absorption of ZnO to enhance the properties of the photodiode.     

罗布泊遥感影像"耳纹"特征分析及其环境意义

研究典型干旱区的罗布泊,对揭示区域环境演变特征和全球变化具有重要意义.从遥感影像上的"耳纹"特征入手,通过光谱、土壤和地表参数等分析,认为:地表全盐含量和结构差异是形成罗布泊遥感影像"耳纹"特征的直接原因;光谱、全盐含量和土壤粒径的分析结果具有很好的一致性."耳纹"记录下了罗布泊地区的环境演变特征,这些特征表明:受全球环境影响,湖水在气候不断干旱的过程中逐渐干涸,干涸过程的气候调整,使罗布泊地区经历了两次相对湿润的气候环境,前一次较长,后一次很短.     

Exact three-body local correlations for excited states of the 1D Bose gas

We derive an exact analytic expression for the three-body local correlations in the Lieb-Liniger model of 1D Bose gas with contact repulsion. The local three-body correlations control the thermalization and particle loss rates in the presence of terms which break integrability, as is realized in the case of 1D ultracold bosons. Our result is valid not only at finite temperature but also for a large class of nonthermal excited states in the thermodynamic limit. We present finite temperature calculations in the presence of external harmonic confinement within local density approximation, and for a highly excited state that resembles an experimentally realized configuration.     

Hydrogenation mechanism in lanthanum-activated magnesium films

With density-functional theory, the dissociative chemisorptions and diffusion processes of hydrogen on both pure and La-doped Mg(0001) surfaces are studied. Calculation results show that the energy barrier obtained for hydrogen dissociation on the La-doped Mg(0001) surface is smaller due to back-donated bonding between molecular H₂ and doped La atom. The obtained diffusion barriers (0.8–0.22 eV) imply a fast motion of atomic H on La-doped Mg(0001) surface.     

Stability and bandwidth enhancement of difference frequencygeneration (DFG)-based wavelength conversion by pump detuning

The authors report on a method for enhancing the operating stability and signal bandwidth of difference-frequency-generation-based wavelength conversion by detuning the pump from the degenerate phase matching wavelength; both can be further enhanced by using nonuniform quasi-phase-matching structures     

Chemical Shift and Its Uses as an Electronic Parameter in Structure-Activity Correlations

Apparent correlations are found between the N-H chemical shifts of congeneric series of compounds and the dipole moments of the molecules, such as lactams and thiolactams, cyclic ureas and thioureas. When there is a high degree of correlation, either the N-H chemical shift or the dipole moment of the molecule can be used as an electronic parameter in correlating the biological activity with the chemical structure. In a series of substituted salicylaldehydes the Hammett σ constant gives better correlation with the biological activity than the O-H chemical shift. This is probably due to the anisotropic effect of the substituent besides the electronic effect. Other factors affecting the N-H chemical shift, e.g. intramolecular hydrogen-bonding of nitrosoureas and the deshielding effect of a benzene ring, in o-phenyleneureas are also presented. In spite of the limitations, the chemical shifts of many compounds can be obtained very easily, therefore, their uses in structure-activity correlations deserve further investigation.