模拟酸雨胁迫与植物叶片光谱反射率特征间的关系

酸雨是一个严重的全球环境问题,中国亚热带地区的严重酸雨污染对森林生态系统的健康构成了潜在的威胁。文章研究了中国亚热带地区常见的6种常绿阔叶树种幼树在不同强度的模拟酸雨(pH 2.5, pH 4.0和pH 5.6)作用下,其叶片的叶绿素含量及可见光部分的光谱反射率的变化特征。结果表明,随模拟酸雨强度的增加,受试树种在pH 2.5和pH 4.0处理下的叶绿素含量均高于pH 5.6的处理;而可见光部分的光谱反射率则普遍低于pH 5.6的处理;pH 2.5和pH 4.0间的差异无显著规律。在经不同强度模拟酸雨作用后,各树种叶片在可见光部分的光谱反射率的差异主要集中在绿光反射峰及红边附近。受试树种对酸雨胁迫均表现出了一定的耐受性,较强的酸雨可在一定程度上对植物生长起到正的生物效应。     

基于叶片高光谱特性分析的树种识别

高光谱遥感技术的出现将为解决森林树种的精细识别难题提供有效的途径。利用高光谱遥感技术进行树种鉴别时,光谱特征的选择及提取是个非常重要的过程。与多光谱数据相比,高光谱数据具有波段多、数据量大、冗余度大等特点。该文利用光谱微分法对原始光谱数据进行处理,分析不同树种原始光谱、光谱一阶微分和光谱二阶微分曲线图,从中选择差异较大的波段用于鉴别不同树种。最后利用欧氏距离对所选择的波段进行检验识别不同树种的效果,检验的结果显示选择的波段能有效地区分不同树种。区分不同树种的有效波段大都位于近红外波段, 并且差异最大的波段也是近红外波段,其分别为1 657～1 666和1 868～1 877 nm。     

Acoustic analysis of a liquefied petroleum gas-fired pulse combustor

Experimental investigation of acoustic characteristics of a Helmholtz type liquefied petroleum gas-fired pulse combustor is presented. In the experiments, the length of the tail pipe was changed from 1.9 m to 1.3 m by 10 cm intervals. Sound level measurements were taken from the exhaust side (outlet) and air flapper side (inlet) at a distance of 1 m from both sides. With decreasing lengths of the tail pipe, the sound pressure level increased. At the measurements related to the exhaust side, the maximum value of equivalent continuous sound pressure level, LEQ was 96.6 dB when the length of the tailpipe and fundamental frequency were 1.3 m and 63 Hz, respectively. Same kinds of measurements were performed at the air flapper side, but the LEQ value was stronger at the exhaust side than the one at the air flapper side. It was also observed that the effect of the type of gaseous fuel on the acoustic efficiency of the pulse combustor can be neglected when the results of the acoustic efficiencies were compared to those in the literature. In order to compare the accuracy of frequencies measured by the sound level meter, a suitable dynamic pressure transducer and a spectrum analyzer were used to perform amplitude and frequency measurements. The average deviation between the measurements performed by the sound level meter and dynamic pressure transducer was 2.4 Hz (3.8% errors) while the average deviation was 3.8 Hz (6% errors) between the sound level meter and spectrum analyzer.     

X射线致HeLa细胞损伤过程中NADPH氧化酶的作用

以HeLa细胞为实验材料, 探讨了NADPH氧化酶在X射线诱导细胞损伤过程中的作用。 结果显示, 12 Gy X射线辐照后细胞内活性氧(ROS)明显增加, 在用NADPH氧化酶抑制剂处理后再辐照, 则细胞内ROS降低到未辐照水平; 同时辐照后NADPH 氧化酶细胞质亚基p47phox 在细胞质积聚并和细胞膜亚基 gp91phox 结合; Western blotting检测结果显示, NADPH 氧化酶的关键亚基 gp91phox 的表达量明显增加。 以上结果说明, NADPH氧化酶可以被X射线激活, 由其介导产生的ROS在X射线诱导HeLa细胞损伤过程中扮演重要角色。 To investigate the role of NADPH oxidase in HeLa cell lesion induced by X ray irradiation, the change of cell survival was detected with MTT assay, reactive oxygen species (ROS) was measured by fluorospectrophotometer. Immunostaining and confocal laser scanning microscopy was employed to detect the co localization of two subunit of NADPH oxidase, p47phox and gp91phox in the cell. Western blotting was used to detect the expression of gp91phox before and after X ray irradiation. After X ray irradiation, intra cellular level of ROS increased obviously. But the increase could be blocked by diphenyleneiodonium (DPI), an inhibitor of NADPH oxidase. Meanwhile, cytosolic subunit p47phox moved to membrane and co localizated with gp91phox after irradiation. Moreover, the results also show that gp91phox increased sharply after 12 Gy X ray irradiation. Therefore, NADPH oxidase mediated production of ROS plays an important role in HeLa cell lesion induced by X ray.     

Raman and IR spectra of the unstable ionic species potassium trimethylsilanolate: The role of the counterion in its theoretical interpretation

We have accomplished a reliable assignment of the vibrational spectra of the ionic species potassium trimethylsilanolate, which is unstable towards hydrolysis and self‐condensation, by means of the combined use of experimental data and theoretical density functional theory (DFT) calculations. We report the first record of the Raman spectrum of the pure solid. Additionally, we have newly recorded its IR spectrum in Nujol mull and for the first time in Fluorolube mull, completing the experimental data available in the literature about this chemical species. Further, in order to discuss the convenience of including the counterion in the model used for the quantum‐mechanical calculations of its vibrational spectra, we have compared the performance of three different theoretical models, namely, the isolated trimethylsilanolate anion, a theoretical monomer of potassium trimethylsilanolate and a simplified ionic cluster model based on its crystalline structure. Copyright © 2007 John Wiley & Sons, Ltd.     

Combustion synthesis and luminescent properties of a new material Li2(Ba0.99,Eu0.01)SiO4:B for ultraviolet light emitting diodes

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li₂(Ba_0.99,Eu_0.01)SiO₄ and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li₂(Ba_0.99,Eu_0.01)SiO₄:B_0.06³⁺ showed 160% improved emission intensity compared with that of the Li₂(Ba_0.99,Eu_0.01)SiO₄ phosphors under UV (λ_ex=350 nm) excitation.     

Temperature dependence of magnetic anisotropy in nanoparticles of CoxFe(3−x)O4

In this paper we present a study of the magnetic anisotropy constant of nanocrystalline magnetic particles of Co_xFe_(3−x)O₄, with x ranging from 0.05 to 1.6, synthesized by a combustion reaction. The magnetic anisotropy constants were obtained by fitting the high-field part of the major hysteresis loops with the law of approach equation down to temperatures of 4 K and up to fields of 60 kOe. The anisotropy constant depends strongly on both temperature and cobalt content x, exhibiting a nonmonotic dome-shaped dependence on x with a maximum at x=1.0. We found that fits at lower temperatures, i.e., 4 and 72 K, give values of K₁ that are approximately one order of magnitude higher than those at higher temperatures, i.e., 272 and 340 K. For example, K₁ for specimens with x=0.8 and 1.0 are 4.21×10⁷ and 4.22×10⁷ ergs/cm³ at 4 K, and 7.64×10⁶ and 7.51×10⁶ ergs/cm³ at 340 K, respectively. Thus, our determination of temperature-dependence of the anisotropy constant represents an improvement over existing works.     

Gas Plasma-Augmented Wound Healing in Animal Models and Veterinary Medicine

The loss of skin integrity is inevitable in life. Wound healing is a necessary sequence of events to reconstitute the body’s integrity against potentially harmful environmental agents and restore homeostasis. Attempts to improve cutaneous wound healing are therefore as old as humanity itself. Furthermore, nowadays, targeting defective wound healing is of utmost importance in an aging society with underlying diseases such as diabetes and vascular insufficiencies being on the rise. Because chronic wounds’ etiology and specific traits differ, there is widespread polypragmasia in targeting non-healing conditions. Reactive oxygen and nitrogen species (ROS/RNS) are an overarching theme accompanying wound healing and its biological stages. ROS are signaling agents generated by phagocytes to inactivate pathogens. Although ROS/RNS’s central role in the biology of wound healing has long been appreciated, it was only until the recent decade that these agents were explicitly used to target defective wound healing using gas plasma technology. Gas plasma is a physical state of matter and is a partially ionized gas operated at body temperature which generates a plethora of ROS/RNS simultaneously in a spatiotemporally controlled manner. Animal models of wound healing have been vital in driving the development of these wound healing-promoting technologies, and this review summarizes the current knowledge and identifies open ends derived from in vivo wound models under gas plasma therapy. While gas plasma-assisted wound healing in humans has become well established in Europe, veterinary medicine is an emerging field with great potential to improve the lives of suffering animals.     

Influences of acoustic instabilities on turbulent-flame propagation

Influences of acoustic instabilities on premixed turbulent-flames have been studied experimentally in a Taylor–Couette (TC) combustor for downward flame propagation in a turbulent flow-field generated in the annulus between two cylinders. Flow-field velocities were measured at a fixed location upstream of the propagating flame using laser-doppler velocimetry, while flame speeds were determined from video-recorded images. It is found that the existence of pre-ignition turbulence in the combustor (generated by rotation of the combustor-cylinder walls) does not eliminate acoustic instabilities, however as the level of pre-ignition turbulence is increased the influence of the secondary acoustic instability on the turbulent-flame speed becomes insignificant. For low intensities of pre-ignition turbulence the flame is found to accelerate during the latter stages of flame propagation, while for high levels of pre-ignition turbulence the flame propagates at a statistically constant speed, even though velocity fluctuations have been substantially amplified by the time the flame reaches the bottom end of the combustor as a result of acoustic instability.     

A NONAUTONOMOUS STAGE-STRUCTURED SINGLE SPECIES MODEL WITH DIFFUSION

1IntroductionRecent1ytheso-calledsinglespeciesm0delwasconsidered,andmanyrcsultshavebeen.bt.in.d[1-7J.In[l],thesinglespeciesmodelwithstage-structtlredinthefOrmofisstudied,whereIi(t)andx.(t)representtheimmatureandmaturepopu-lati0nsdensitiesrespectively;ofisthe0bservedorassumedbirthrateofxi(t)attimet(-T5t5O),andTrepresentsac0nstanttime1engthfortheiITl-maturetobecomematurity.aisthebirthrateofmaturepopulation.7isthedeathrateofimmaturepopulationandfiistheLogisticconstantofthemature.Somesufficien…