Constituents of the Whole Herb of Clinoponium laxiflorum

The isolation and identification of twenty‐two components (including one new compound) from the whole herb of Clinoponium laxiflorum (Hay) Matsum (Labiatae) are described. Their structures were determined on the basis of spectral and chemical transformation. One new compound is methyl rosmarinate. The other twenty‐one compounds include three steroids (α‐spinasterol, α‐spinasteryl‐3‐O‐β‐D‐glucopyranoside, and β‐sitosteryl‐3‐O‐β‐glucopyranoside), three triterpenes (oleanolic acid, ursolic acid, and betulinic acid), nine flavonoids (didymin, apigenin‐7‐O‐β‐glucopyranoside, luteolin‐7‐O‐β‐glucopyranoside, isosakuranetin, narigenin, apigenin, luteolin, narirutin, and hesperidin), three lignolic acids (rosmarinic acid, 3‐(3,4‐dihydroxyphenyl)lactic acid, and caffeic acid), and three phenols (4‐hydroxybenzaldehyde, 3,4‐dihydroxybenzaldehyde, and 3,4‐dihydroxybenzoic acid).     

A fast encoding algorithm for fractal image compression using theDCT inner product

In this paper, a fast encoding algorithm is developed for fractal image compression. At each search entry in the domain pool, the mean square error (MSE) calculations of the given range block and the eight dihedral symmetries of the domain block are obtained simultaneously in the frequency domain, in which the redundant computations are all eliminated in the new encoding algorithm. It is shown in software simulation that the encoding time is about six times faster than that of the baseline method with almost the same PSNR for the retrieved image. The fast algorithm is performed to deal with the eight dihedral symmetries at each search entry. Therefore, it can be applied to various enhanced algorithms which are equipped with quadtree, classification, and other mechanisms.     

Low-frequency noise properties of dynamic-threshold (DT) MOSFET's

This paper shows that MOSFET operated in dynamic-threshold (DT) mode (V_body=V_gate) is more suitable for low-noise RF/analog applications than those operated in conventional mode (V_body=V_source). Detailed low-frequency noise properties of these two modes of device operation were compared for 0.31-μm gate MOSFET's, in which NMOS's are surface-channel devices (S.C.) and PMOS's are buried-channel (B.C.) devices. Experimental data show that when the devices are biased at same transconductance, the low-frequency noise in DT mode is 30 times lower (at g_m=2.2×10^-3 S) than that in the conventional mode for the B.C. devices and ten times (at g_m=2.0×10 ^-3 S) lower for the S.C. devices     

Defect engineering by synchrotron radiation X‐rays in CeO2 nanocrystals

This work reports an unconventional defect engineering approach using synchrotron‐radiation‐based X‐rays on ceria nanocrystal catalysts of particle sizes 4.4–10.6 nm. The generation of a large number of oxygen‐vacancy defects (OVDs), and therefore an effective reduction of cations, has been found in CeO₂ catalytic materials bombarded by high‐intensity synchrotron X‐ray beams of beam size 1.5 mm × 0.5 mm, photon energies of 5.5–7.8 keV and photon fluxes up to 1.53 × 10¹² photons s^?1. The experimentally observed cation reduction was theoretically explained by a first‐principles formation‐energy calculation for oxygen vacancy defects. The results clearly indicate that OVD formation is mainly a result of X‐ray‐excited core holes that give rise to valence holes through electron down conversion in the material. Thermal annealing and subvalent Y‐doping were also employed to modulate the efficiency of oxygen escape, providing extra control on the X‐ray‐induced OVD generating process. Both the core‐hole‐dominated bond breaking and oxygen escape mechanisms play pivotal roles for efficient OVD formation. This X‐ray irradiation approach, as an alternative defect engineering method, can be applied to a wide variety of nanostructured materials for physical‐property modification.     

Unveiling the Nanoparticle‐Seeded Catalytic Nucleation Kinetics of Perovskite Solar Cells by Time‐Resolved GIXS

Recently, a new seeding growth approach for perovskite thin films is reported to significantly enhance the device performance of perovskite solar cells. This work unveils the intermediate structures and the corresponding growth kinetics during conversion to perovskite crystal thin films assisted by seeding PbS nanocrystals (NCs), using time‐resolved grazing‐incidence X‐ray scattering. Through analyses of time‐resolved crystal formation kinetics obtained from synchrotron X‐rays with a fast subsecond probing time resolution, an important “catalytic” role of the seed‐like PbS NCs is clearly elucidated. The perovskite precursor‐capped PbS NCs are found to not only accelerate the nucleation of a highly oriented intermediate phase, but also catalyze the conversion of the intermediate phase into perovskite crystals with a reduced activation energy E_a = 47 (±5) kJ mol^?1, compared to 145 (±38) kJ mol^?1 for the pristine perovskite thin film. The reduced E_a is attributed to a designated crystal lattice alignment of the perovskite nanocrystals with perovskite cubic crystals; the pivotal heterointerface alignment of the perovskite crystals coordinated by the Pb NCs leads to an improved film surface morphology with less pinholes and enhanced crystal texture and thermal stability. These together contribute to the significantly improved photovoltaic performance of the corresponding devices.     

A new decoding algorithm for correcting both erasures and errors of Reed-Solomon codes

In this paper, a high efficient decoding algorithm is developed here in order to correct both erasures and errors for Reed-Solomon (RS) codes based on the Euclidean algorithm together with the Berlekamp-Massey (BM) algorithm. The new decoding algorithm computes the errata locator polynomial and the errata evaluator polynomial simultaneously without performing polynomial divisions, and there is no need for the computation of the discrepancies and the field element inversions. Also, the separate computation of the Forney syndrome needed in the decoder is completely avoided. As a consequence, the complexity of this new decoding algorithm is dramatically reduced. Finally, the new algorithm has been verified through a software simulation using C/sup ++/ language. An illustrative example of (255,239) RS code using this program shows that the speed of the decoding process is approximately three times faster than that of the inverse-free Berlekamp-Massey algorithm.     

The use of aryl azido ATP analogs as photoaffinity labels for myosin ATPase.

The synthesis of ATP analogs containing a photoactive aryl azido grouping coupled to the 3' hydroxyl of ATP is described. The potential effectiveness of these analogs in the investigation of nucleotide-binding regions is outlined and this effectiveness demonstrated by their photodependent inhibition of subfragment 1 ATPase. The use of 14C-labeled azido ATP demonstrates an almost stoichiometric covalent binding of the analog. Because of their potential application to other systems, a number of reactions describing the reactivity of the 3' hydroxyl of the nucleotide ribose are outlined in an Appendix.     

Near-field scattering by physical theory of diffraction andshooting and bouncing rays

This paper proposes a method to compute the near-field RCS and Doppler spectrum of a target when the distances to the antennas are comparable to the target size. By dealing with a small piece of the target surface at a time, the transmitting antenna, and the receiving antenna are in the far-field zone of the small piece of the induced currents. The electromagnetic field produced by this small piece of induced currents can be written as a spherical wave. Sum up all spherical waves produced by every small piece of induced currents and we can obtain the total scattered field at the receiving antenna. The physical theory of diffraction (PTD) and the method of shooting and bouncing rays (SBR) are modified to evaluate the received signals. Numerical results based on these techniques are obtained and discussed. The formulation applies the simple concepts of “equivalent” image and vector effective height, which are believed to be novel     

Fast codeword search technique for the encoding of variable-ratevector quantisers

The authors present a fast search algorithm for the encoding of variable-rate vector quantisers (VQs). The optimal encoder for the variable-rate full-search VQs considers both the squared distance and channel index length for the search of codewords. Therefore, the existing fast search algorithms for the fixed-rate full-search VQs might not be able to effectively reduce the computational complexities for the variable-rate VQs. An algorithm is presented which solves this problem using a two-stage search process. A large number of undesired codewords are removed at the first stage of the search with a small computational overhead. At the second stage, the optimal codeword are searched among the remaining codewords using the partial distance search technique in the transform domain. Simulation results show that the algorithm is more effective than other fast search algorithms for the variable-rate VQs     

Reflection and transmission characteristics of single-layerperiodic composite structures for TE case

A periodic surface-integral formulation is proposed to analyze the reflection and transmission characteristics of a single-layer lossy periodic composite structure for the TE case. Theoretically, the equivalence principle, involving unknown electric and magnetic currents over material discontinuity interfaces, the structure periodicity, and the Poisson summation formula are used to reduce the problem to a periodic cell. These surface-integral equations are solved numerically by the method of moments with pulse bases and point matching. In this study, the numerical results such as reflected, transmitted, and dissipated powers for a single-layer graphite/epoxy composite structure with both circular and square fibers are presented for the TE case. The effects of frequency, incident angle, fiber area, fiber conductivity, and embedding dielectric etc. are examined in detail. Convergence study and comparison with the previous published results are also included to confirm the accuracy of the new formulation