Flavonoids isolated from Draconis Resina

One new chalcone, 4,6-dihydroxy-2-methoxy-3-methyldihydrochalcone (4), together with four known compounds, dammaradienol (1), (-)-5-methoxyflavan-7-ol (2), 5-methoxy-6-methyl-2-phenyl-7H-chromen-7-one (3), and dracorhodin (5), were isolated from Draconis Resina. The structures of these compounds were determined by spectral methods. Among these five compounds, compounds 1, 2, and 3 exhibited cytotoxicity against KB and HepG2 cells.     

Ultra-broadband OFDM signal generation for 1-Tb/s super-channel coherent optical OFDM transmission

A 320.6-GHz multi-band optical OFDM signal generation scheme consisting of continuous 4,104 subcarriers is demonstrated for 1-Tb/s coherent optical OFDM (CO-OFDM) transmission. The 36 uncorrelated orthogonal bands are generated using a recirculating frequency shifter (RFS) with single laser by adjusting the loop delay of RFS to be an integer multiple of OFDM symbol period. The principle and performance of this generation scheme is studied theoretically and experimentally. The 1-Tb/s CO-OFDM signal is successfully received after 600-km SSMF fiber transmission without any dispersion compensation.     

General shape control of colloidal CdS, CdSe, CdTe quantum rods and quantum rod heterostructures

We report a general synthetic method for the formation of shape-controlled CdS, CdSe and CdTe nanocrystals and mixed-semiconductor heterostructures. The crystal growth kinetics can be manipulated by changing the injection rate of the chalcogen precursor, allowing the particle shape-spherical or rodlike-to be tuned without changing the underlying chemistry. A single injection of precursor leads to isotropic spherical growth, whereas multiple injections promote epitaxial growth along the length of the c-axis. This method was extended to produce linear type I and type II semiconductor nanocrystal heterostructures.     

Extended-Kalman-filter-based chaotic communication

Together with the optimal linearization technique, an extended-Kalman-filter-basedchaotic communication is first proposed in this paper. First,the optimal linearization technique is utilized to find theexact linear models of the chaotic system at operating statesof interest. Then, an extended Kalman filter (EKF) algorithmis used to estimate both the parameters and states where themessage is already embedded. By using the EKF together withthe optimal linear model, the message can be recovered wellat the receiver's end. Numerical examples and simulations aregiven to show the effectiveness of the proposed methodology.     

Energy and variational principles for generalized (gyroscopic) conservative problems

The study of the local stability of the equilibrium of an elastic body subjected to conservative and gyroscopic forces, which was initiated in [6] is extended. Two variational principles are established in actual and equivalent energy terms respectively. These principles, together with the stability criterion formulated in [6], form a generalized version of (and reduce to) the classical energy principles governing the stability of conservative non-gyroscopic systems, and are applied to the example of a loaded (or unloaded) elastic shaft under constant rotation. In addition, a necessary and sufficient condition for the applied forces to be gyroscopic or conservative is obtained explicitly as a function of the change in force components due to a small disturbance superimposed on the equilibrium state.     

Microstructure and photoluminescence of Ge-doped mesoporous silica

Nanostructured Ge-doped mesoporous silica powder and thin film were prepared with a cetyltrimethylammonium bromide self-assembled template to investigate the doping effects on the structure and optical properties of mesoporous silica. The X-ray diffraction, transmission electron microscopy and photoluminescence (PL) results suggest that the Ge-doped mesoporous silica with Ge/Si molar ratio of 0.01 was characterized by the strongest PL intensity without phase separation. Worm-like Ge-doped porous silica with specific area up to 987 m²/g could be obtained in this study, in which some Si atoms were replaced by Ge atoms according to the X-ray photoelectron spectroscopy analyses. The PL intensity of mesoporous silica could be increased by germanium-induced oxygen-related defects, but for the samples with Ge/Si molar ratios larger than 0.01, the PL intensity decreased due to the phase separation of germanium oxide.     

An approach in exploring the fundamental dosimetric characteristics for a long shelf life irradiated acrylamide-based gel

In this study, a long shelf life irradiated gel made from a low-toxicity N-isopropylacrylamide (NIPAM) monomer was used to study the dosimetric characteristics associated with magnetic resonance imaging (MRI). Specifically, the Taguchi method was utilized to investigate the influence of MRI scanning parameters on the performance objectives of NIPAM gels, and the priorities of the parameters that influence the process were determined using Delta statistics. The influence of different echo spacing on the relaxation rate–dose response of the gel and the relationship among the dose resolution (D _Δ ^P ), dose accuracy, and reproducibility were also examined. The results indicated that the repetition time (TR) and echo time (TE), having Delta values of 3.81042 and 4.52752, respectively, were the most influential factors. Analysis of variance further confirmed that TE was the major factor, with a percentage contribution of 58.36 %, and TR was the second factor with a percentage contribution of 41.34 %. The maximum sensitivity was 0.1506 s^?1 Gy^?1 from 0 to 15 Gy, and the best D _Δ ^P of the NIPAM gel was 0.017 Gy. Two months after the irradiation, no obvious changes in linearity and sensitivity were observed, indicating that the NIPAM gels are highly stable. The gel dosimeters were also applied in comparing the planar dose distributions of the gel dosimeters and treatment planning system. The comparison showed good agreement of isodose lines on selected planes in the transverse plane. This result indicates the great potential of the NIPAM dosimeter has a clinical dose verification tool.     

Continuous to discrete model conversion for the system with a singular system matrix based on matrix sign function

The analytic continuous to discrete model conversion for the system with a singular system matrix based on the computationally fast and numerically stable sign function is firstly presented in this note. The proposed methodology yields a more accurate model conversion than existing approximate methods. An illustrative example is presented to show the accuracy of the proposed methodology.     

Incomplete Inverse Spectral and Nodal Problems for Differential Pencils

We prove uniqueness theorems for so-called half inverse spectral problem (and also for some its modification) for second order differential pencils on a finite interval with Robin boundary conditions. Using the obtained result we show that for unique determination of the pencil it is sufficient to specify the nodal points only on a part of the interval slightly exceeding its half.