阿尔及利亚激光和激光等离子体研究概况

应阿尔及利亚国家科学研究组织的邀请，中国科学院激光考察组一行四人于1981年6月10日到邡日进行了为期两周的访问。考察组受到阿方热情接待，先后在阿尔及尔、君士坦丁和赛迭夫三个城市考察了与激光、光学有关的大学和科学研究中心。在核科学技术研究中心(CSTN)作了三天学术报告。与阿专家共同讨论研究，选择了阿从法国进口的高功率钕玻璃激光系统的安装场地，并制定了方案。双方专家就中阿今后在激光及激光等离子体研究方面的合作问题交换了意见。阿尔及利亚政府对教育和科学的高度重视，先进的仪器设备和专业人材匮乏的矛盾，以及和我国合作研究的热忱愿望等都给我们留下深刻的印象。     

Molecular magnetic properties of heteroporphyrins: a theoretical analysis

B3LYP/6-31G(d) optimization of porphyrin, tetraphenylporphyrin and their 21,23-diheteroatom substituted derivatives with O, S, and Se heteroatoms was performed. A planar macrocycle was found in all cases except 21,23-dioxatetraphenylporphyrin which presents only slight deviations from planarity. A Bader analysis uncovers the presence of S-S and Se-Se interactions in the four corresponding heteroporphyrins, which appreciably distort the original unsubstituted macrocycles. In the minimum energy structures of heterotetraphenylporphyrins the four meso phenyl groups slant alternatively to right or left so that the two pairs of opposite phenyls present a staggered conformation. The pi current induced by a perpendicular magnetic field in porphyrin bifurcates across both types of pyrrole subunits but the presence of O, S and Se heteroatoms in 21,23-diheteroporphyrins causes a diminution of the current density through the inner section of the two heterorings and, consequently, the current path goes then through the outer section of these rings. The NICS values at the ring critical points of the heterorings are much larger (in absolute value) than those at the pyrrole ring critical points but appreciably smaller than that at the ring critical point of a pyrrole molecule. In agreement with experimental data the (1)H NMR present appreciable downfield shifts for the beta H atoms of the heterorings in the 21,23-heterosubstituted molecules.     

4G基站设备2011年支出将达30亿美元

据研究机构ABI Research日前预测：随着4G商用和频谱的再利用,无线基础设施市场必会异常火爆。预计4G基站设备支出2011年将达到30亿美元左右,2016年可能达到165亿美元。2011年将有近32000个基站被升级改造,用以支持4G商用服务。另将有约19000个新基站被部署,     

1,3-dipolar cycloadditions from tricyclic hemiaminals. Synthesis of the quinocarcin core through catalyst-free generation of azomethine ylides

The generation of azomethine ylides from the readily accessible hemiaminals 3 and 8 or from iminium salt 10 was studied. Compounds 8 gave anti- and syn-cycloadducts containing the quinocarcin core through a catalyst-free dehydration process.     

Synthesis of benzo- and naphtho-fused bicyclo[n.3.1]alkane frameworks with a bridgehead nitrogen function by palladium-catalyzed intramolecular α'-arylation of α-nitroketones

The C-alkylation of cyclic α-nitroketones with α-halobenzyl halides in the presence of DBU followed by a Pd-catalyzed intramolecular C-arylation afforded benzo-and naphtho-fused bicyclo[n.3.1]alkane derivatives (n = 3, 4, 5) in excellent overall yields for the two-step sequence. In some of the reactions starting from α-nitrocyclooctanone, the major products were fused indane derivatives arising from an intramolecular attack of an intermediate Pd species onto the carbonyl group, followed by elimination.     

Rupture kinetics of liquid bridges during a pulling process: a kinetic density functional theory study

Capillary bridge is a common phenomenon in nature and can significantly contribute to the adhesion of biological and artificial micro- and nanoscale objects. Especially, it plays a crucial role in the operation of atomic force microscopy (AFM) and influences in the measured force. In the present work, we study the rupture kinetics and transition pathways of liquid bridges connecting an AFM tip and a flat substrate during a process of pulling the tip off. Depending on thermodynamic conditions and the tip velocity, two regimes corresponding to different transition pathways are identified. In the single-bridge regime, the initial equilibrium bridge persists as a single one during the pulling process until the liquid bridge breaks. While, in the multibridge regime the stretched liquid bridge transforms into an intermediate state with a collection of slender liquid bridges, which then break gradually during the pulling process. Moreover, the critical rupture distance at which the bridges break changes with the tip velocity and thermodynamic conditions, and its maximum value occurs near the boundary between the single-bridge regime and the multibridge regime, where the longest range capillary force is produced. In this work, the effects of tip velocity, tip size, tip-fluid interaction, and humidity on rupture kinetics and transition pathways are also systematically studied.     

Rapid control of switchable oil wettability and adhesion on the copper substrate

We described a facile approach to rapidly achieve the reversible oil wettability and adhesion transition on the copper substrate. Plasma treatment and surface fluorination were used to tune the surface composition, and this tunability of the surface composition, along with the stable surface roughness, gave rise to the switchable wettability varying from superoleophobicity to superoleophilicity and reversible oil adhesion between sliding superoleophobicity and sticky superoleophobicity. It took only 1.25 min to realize the whole wettability transition and 5 min for the whole adhesion transition. Additionally, the application of a sticky superoleophobic surface was demonstrated. This study represents an important addition to the field of functional superoleophobic materials.     

Brief, efficient and highly diastereoselective synthesis of (±)-pumiliotoxin C based on the generation of an octahydroquinoline precursor via a four-component reaction

A short and highly diastereoselective synthesis of the amphibian alkaloid pumiliotoxin C is described, based on the preparation of an octahydroquinoline derivative through a four-component reaction. The route proceeds in 66% overall yield from 1,3-cyclohexanedione and includes two hydrogenation steps, whose stereochemical outcome was controlled via nitrogen acylation.     

Exchange bias in iron oxide nanoclusters

Iron oxide nanoclusters have been prepared by the gas-phase aggregation technique to form thin film structures with very high exchange bias values (up to 3000?Oe at low temperatures). Composition has been analysed by x-ray absorption and M?ssbauer spectroscopies in order to elucidate the actual origin of the observed magnetic behaviour. The formation of a metal-oxide core-shell arrangement to explain the observed exchange bias has to be discarded since results show no metallic iron content and the main presence of α-Fe(2)O(3). The observed weak ferromagnetism and exchange bias are in agreement with the obtained size of α-Fe(2)O(3) nanoparticles: weak ferromagnetism because of the well-known spin canting in this antiferromagnetic structure and exchange bias because of the interaction between different spin sublattice configurations promoted by the modification of iron coordination in α-Fe(2)O(3) nanoparticles. Moreover, the preparation method is proposed for tuning both magnetization and exchange bias values by modification of the preparation conditions of α-Fe(2)O(3) nanoparticles, which open new possibilities in the design of new materials with required properties.     

Application of wavelet transform on improving detecting precision of the non-invasive blood components measurement based on dynamic spectrum method

Time-varying noises in spectra collection process have influence on the prediction accuracy of quantitative calibration in the non-invasive blood components measurement which is based on dynamic spectrum (DS) method. By wavelet transform, we focused on the absorbance wave of fingertip transmission spectrum in pulse frequency band. Then we increased the signal to noise ratio of DS data, and improved the detecting precision of quantitative calibration. After carrying out spectrum data continuous acquisition of the same subject for 10 times, we used wavelet transform de-noising to increase the average correlation coefficient of DS data from 0.979 6 to 0.990 3. BP neural network was used to establish the calibration model of subjects' blood components concentration values against dynamic spectrum data of 110 volunteers. After wavelet transform de-noising, the correlation coefficient of prediction set increased from 0.677 4 to 0.846 8, and the average relative error was decreased from 15.8% to 5.3%. Experimental results showed that the introduction of wavelet transform can effectively remove the noise in DS data, improve the detecting precision, and accelerate the development of non-invasive blood components measurement based on DS method.