Kuroshines A and B,new alkaloids from Zoanthus kuroshio

A chemical investigation of Zoanthus kuroshio has yielded two new alkaloids, kuroshines A (1) and B (2). The compounds possess a densely functionalized ring system on the basis of the zoanthamine frames. The structures of 1 and 2 were elucidated through interpretation of spectroscopic methods, especially 2D NMR techniques (COSY, HMQC, HMBC, and ROESY). The absolute stereochemistry of 1 was further confirmed by an X-ray single crystallographic analysis using a mirror Cu-Kα radiation.     

Quantification and Optimization of Ethanolic Extract Containing the Bioactive Flavonoids from Millettia pulchra Radix

Millettia pulchra is traditionally used for treating diseases, including joint pain, fever, anemia, and allergies. It is also a potential resource of natural flavonoid derivatives, which represents major constituents of this plant. This study aimed to isolate the major compounds from M. pulchra radix, develop and validate the HPLC-PDA method to determine their contents, and optimize its extraction. Four major flavonoid derivatives (karanjin, lanceolatin B, 2”,2”-dimethylpyrano-[5″,6″:7,8]-flavone, and pongamol) were isolated using silica gel column chromatography, crystallization techniques in large amounts with high purities (>95%). A simple, accurate high-performance liquid chromatography–photodiode array (HPLC–PDA) detection method has been developed and validated with significantly statistical impacts according to International Conference on Harmonization (ICH) guidelines. The Response Surface Methodology (RSM), Artificial Neural Network (ANN) models were employed to predictive performance and optimization of the extraction process. The optimized conditions for the extraction of major flavonoids were: extraction time (twice), solvent/material ratio (9.5), and ethanol concentration (72.5%). Our research suggests an effective method, which will be helpful for quality control in the pharmaceutical development of this species.     

Schinarisanlactone A, a new bisnortriterpenoid from Schisandra arisanensis

A novel triterpenoid, schinarisanlactone A (1), was isolated from the fruits of Schisandra arisanensis. Compound 1 possesses an unprecedented skeleton having a 5/7/7/5/7/5/6/5-fused octacyclic ring system. The structure of 1 was determined by 2D NMR techniques (COSY, HMQC, HMBC, and NOESY) and was confirmed by X-ray crystallographic analysis. Schinarisanlactone A (1) exhibited significant anti-HIV activity.     

Theoretical analysis of transient waves in a simply-supported Timoshenko beam by ray and normal mode methods

The dynamic transient responses of a simply-supported Timoshenko beam subjected to an impact force are investigated by two theoretical approaches – ray and normal mode methods. The mathematical methodology proposed in this study for the ray method enable us to construct the solution for the interior source problem and to extend to solve the complicated problem for the multi span of the Timoshenko beam. Numerical results based on these two approaches are compared. The comparison in this study indicates that the normal mode method is more computationally efficient than the ray method except for very short time after the impact. The long-time transient responses are easily calculated using the normal mode method. It is shown that the average long-time transient response converges to the corresponding static value. The Timoshenko beam theory is more accurate than the Bernoulli–Euler beam theory because it includes shear and rotary inertia. This study also provides the slender ratio for which the Bernoulli–Euler beam can be used for the transient-response analysis of the displacement. Moreover, the resonant frequencies obtained from finite element calculation based on the three-dimensional model are compared with the results calculated using the Timoshenko beam and Bernoulli–Euler beam theories. It is noted in this study that the resonant frequency can be accurately determined by the Timoshenko beam theory if the slender ratio is larger than 100, and by the Bernoulli–Euler beam theory if the slender ratio is larger than 400.     

Synthesis and solid-state NMR characterization of cubic mesoporous silica SBA-1 functionalized with sulfonic acid groups

Well-ordered cubic mesoporous silicas SBA-1 functionalized with sulfonic acid groups have been synthesized through in situ oxidation of mercaptopropyl groups with H(2)O(2) via co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) templated by cetyltriethylammonium bromide (CTEABr) under strong acidic conditions. Various synthesis parameters such as the amounts of H(2)O(2) and MPTMS on the structural ordering of the resultant materials were systematically investigated. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), multinuclear solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, (29)Si{(1)H} 2D HETCOR (heteronuclear correlation) NMR spectroscopy, thermogravimetric analysis (TGA), and nitrogen sorption measurements. By using (13)C CPMAS NMR technique, the status of the incorporated thiol groups and their transformation to sulfonic acid groups can be monitored and, as an extension, to define the optimum conditions to be used for the oxidation reaction to be quantitative. In particular, (29)Si{(1)H} 2D HETCOR NMR revealed that the protons in sulfonic acid groups are in close proximity to the silanol Q(3) species, but not close enough to form a hydrogen bond.     

Transient wave analysis of a cantilever Timoshenko beam subjected to impact loading by Laplace transform and normal mode methods

This study applies two analytical approaches, Laplace transform and normal mode methods, to investigate the dynamic transient response of a cantilever Timoshenko beam subjected to impact forces. Explicit solutions for the normal mode method and the Laplace transform method are presented. The Durbin method is used to perform the Laplace inverse transformation, and numerical results based on these two approaches are compared. The comparison indicates that the normal mode method is more efficient than the Laplace transform method in the transient response analysis of a cantilever Timoshenko beam, whereas the Laplace transform method is more appropriate than the normal mode method when analyzing the complicated multi-span Timoshenko beam. Furthermore, a three-dimensional finite element cantilever beam model is implemented. The results are compared with the transient responses for displacement, normal stress, shear stress, and the resonant frequencies of a Timoshenko beam and Bernoulli–Euler beam theories. The transient displacement response for a cantilever beam can be appropriately evaluated using the Timoshenko beam theory if the slender ratio is greater than 10 or using the Bernoulli–Euler beam theory if the slender ratio is greater than 100. Moreover, the resonant frequency of a cantilever beam can be accurately determined by the Timoshenko beam theory if the slender ratio is greater than 100 or by the Bernoulli–Euler beam theory if the slender ratio is greater than 400.     

利用气泡探测器测量激光快中子

在利用超强激光驱动中子源的研究和应用研究中,中子源的产额及其角分布至关重要.我们在星光Ⅲ号激光装置上采用气泡探测器对强激光驱动的中子源的产额及其角分布进行了测量.利用超强皮秒激光与碳氘薄膜靶相互作用产生高能氘离子束撞击次级碳氘靶,通过氘-氘核反应产生准单能快中子.实验发现中子束的发射具有一定的方向性,在入射氘离子的传输方向上中子束具有更高的强度,测量得到的中子束最大强度为5.13×10⁷ n/sr.利用实验测量的氘离子能谱和角分布对中子束角分布进行了理论计算,结果与实验测量基本一致.     

Linear stochastic singular control problems

The explicit feedback control law for the singular linear-quadratic-gaussian stochastic control problem is derived. The interesting implication of the control law in terms of information pattern is discussed.The research reported in this document was done while the author was a Guggenheim Fellow at the Imperial College, London, England, and was supported in part by the U.S. Army Research Office, the U.S. Air Force Office of Scientific Research, and the U.S. Office of Naval Research under the Joint Services Electronics Program, Contracts Nos. N00014-67-A-0298-0006, 0005, and 0008. The author is indebted to various discussions with D. Q. Mayne and J. M. C. Clark of Imperial College which clarified several points.     

自由运转半导体激光器边模间的强度关联

半导体激光器的强度和相位起伏一直是影响其应用的关键所在.在实验上研究了自由运转模式下半导体激光器的强度噪声.采用自制的分辨率为0.01 nm的光谱仪成功地分辨出数十个边模，并利用射频低噪声光电探测器系统，分析了激光器的主模与边模之间以及各边模之间的强度噪声关联特性.从实验上证实了主模与边模之间的负关联效应，同时观察到边模之间存在的周期性负关联.该结果对进一步认识半导体激光器噪声的产生机制及强度压缩光的产生机制具有重要意义. 关键词： 半导体激光器 强度噪声 负关联     

Four new nonaoxygenated C18 dibenzocylcooctadiene lignans from Kadsura philippinensis

Four new nona-oxygenated C18 dibenzocyclooctadiene lignans, kadsuphilins C-F (1-4), were isolated from the EtOAc soluble portion of the alcoholic extract of the aerial parts of Kadsura philippinensis. The structures of 1-4 were elucidated on the basis of extensive spectroscopic analyses, including 2D NMR (HMQC, HMBC, and NOESY) experiments, comparison of the spectral data with those of the related metabolites. The stereochemistries of the biphenyl and octadiene moieties were deduced from circular dichorism (CD) and the NOESY spectra, respectively. The in vitro antiplatelet aggregation activity of metabolites 1-4 also have been evaluated.