[en] Using rare earth coordination polymers with salicylic acid and rare earth nitrates as precursors for the luminescent species Y_xGd_2-xO₃:Eu³⁺, composed with the polyvinyl alcohol (PVA) as dispersing media, nanophosphors of Y_xGd_2-xO₃:Eu³⁺ with different ratio of Y and Gd were synthesized, among x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.6, 1.8 for rare earth nitrate precursors and x = 0.4, 1.0, 1.6 for rare earth salicylate coordination polymer precursors, respectively. X-ray diffraction (XRD) and scanning electronic microscope (SEM) show that these materials have the nanometer size of 20-70 nm. These nanometer materials exhibit strong emission at 612 nm and a blue shift of 6 nm compared with the bulk Y₂O₃:Eu³⁺ phosphors

[en] The energy of the first excited state of quantum-well infrared detectors plays an important role in determining performance. The uncertainties in material and growth parameters make it difficult to design quantum-well detectors with a precise control of the location of energy states. Such uncertainties will cause detectors to be either bound to continuum or bound to bound. In this article, we present a technique to locate the excited-state position in bound-to-bound quantum-well infrared detectors by measuring the bias dependence of the photoresponse. We have employed an InGaAs/AlGaAs quantum-well detector operating near 5 μm for this study. The photocurrent was found to have a strong bias dependence indicating the infrared transition in the quantum well is bound to bound in nature. The bias dependence of the photoresponse was compared with theoretical estimates including the tunneling of photoexcited electrons through the barrier. The results showed a good agreement and this allowed us to determine the location of the excited state from the barrier edge. copyright 2001 American Institute of Physics

[en] Pt/PbZr_0.53Ti_0.47O₃ (PZT)/LaAlO₃ (LAO)/Si and Pt/PbZr_0.53Ti_0.47O₃/La_0.85Sr_0.15CoO₃ (LSCO)/LaAlO₃/Si structures for ferroelectric field effect memory applications were fabricated on n-type Si substrate by pulsed laser deposition (PLD). The Auger electron spectrometry (AES) analysis shows that a LaAlO₃ buffer layer can effectively prevent Si and Ti, Pb interdiffusion between PZT and Si substrate. For both of the structure, the current density-voltage measurement shows a typical leakage current density of about 10^-7 A/cm² at 8 V applied voltage. Furthermore, it has been demonstrated that the PbZr_0.53Ti_0.47O₃/LaAlO₃/Si structures and Pt/PbZr_0.53Ti_0.47O₃/La_0.85Sr_0.15CoO₃/LaAlO₃/Si structures exhibit ferroelectric switching properties, showing a memory window as large as 2 and 2.9 V, respectively, under a ramp rate of 200 mV/s from -6 to +6 V driving voltage at 1 MHz. It is believed that the La_0.85Sr_0.15CoO₃ buffer layer deposited on LaAlO₃ layer can improve the crystalline properties of PZT films, and then result in lager polarization of PZT and lager memory windows for Pt/PbZr_0.53Ti_0.47O₃/La_0.85Sr_0.15CoO₃/LaAlO₃/Si structures

[en] We extract the magnetic polarizability from the quadratic response of a hadron's mass shift in progressively small static magnetic fields. The calculation is done on a 24 x 12 x 12 x 24 lattice at a = 0.17 fm with an improved gauge action and the clover quark action. The results are compared to those from experiments and models where available

[en] Experiment 91-12 is a study of elastic and quasi-free (e,e'p) scattering using the AmPS electron storage/stretcher ring at NIKHEF and a tensor polarized deuterium internal target. A beam of approximately 10¹⁶ atoms/s of tensor polarized deuterium, produced in an atomic beam source (ABS), was fed into a cooled storage cell and a large acceptance non-magnetic detector system was used to detect electrons in coincidence with protons, or deuterons. Data have been taken at a beam energy of 565 MeV, with beam currents up to 125 mA (corresponding to a luminosity of 10³¹ atoms/cm²s), and with the polarization direction parallel and perpendicular to the momentum transfer. Results for the observables T_ij will be presented for both elastic and quasi-free scattering kinematics for four-momentum transfers in the range 0.1< Q²<0.3(GeV/c)² and missing momenta up to 200 MeV/c. In PWIA, these observables vanish in the absence of D-wave contributions to the deuteron ground-state wave functions

[en] Breeding system and pollination biology of Paeonia delavayi (Peaoniaceae) from Shangri-La, Yunnan Province, southwest of China were studied. Flowering phenologies and flower visitors were observed or collected from 2008 to 2011. The pollen viability, stigma receptivity and pollination efficiency of different visitors were detected and tested. The florescence lasted for 6- 9d in a single flower from mid-May to late June. A high percentage of flower damage promoted early anther dehiscence. Flowers started disseminating pollen at 1-2 d after flowering, and lasted for 5-6 d. Pollen viability could be preserved for more than 10 d at normal temperature. High seed rate from the stigma was observed at 1 d before flowering to 3d after flowering, and the dissemination hysteresis was defined as protogyny. The P/O ratios were 6,124 to 9,713:1, suggesting that the larger quantity of pollen to increased the seed setting rate. Three species of bees, eight species of beetles, seven species of syrphid flies, four species of ants, and three species of butterflies were observed on the flowers. P. delavayi rewarded to the visitors by releasing fragrance, providing pollen and nectar. On the bodies of the visitors under stereomicroscope and scanning electron microscope (SEM), much pollen from the plants of similar flowering period inner community were found which indicated that these incompatible visitors were not species-specific pollinators. The bagging experiments showed that P. delavayi was selfincompatible and no apomixes. Anemophily only played a minor role in the fertilization. A few seeds with poor plumpness can be produced by geitonogamy. Seed setting rate of artificial xenogamy was higher than natural pollination. Artificial control of the visitors' species showed bees being the most important pollinators. Beetles and ants participated in pollination to someextent and were unstable. Syrphid flies and butterflies were very unreliable with low pollination efficiency. Reproductive success depended largely on cross-pollination assisted by pollinator activities, especially the bees. (author)

[en] To analyze the flux pinning in high temperature superconductors (HTS) more accurately at high temperature such as 77 K, an improved method based on the Dew-Hughes model has been developed. Assumed that core pinning is dominant in HTS, point, surface and volume pinning center in samples caused by normal phase and spatial variations of the Ginzburg parameter (Δκ) have been considered. As examples, the pinning forces of several Bi-2223 silver sheathed (Bi-2223/Ag) tapes have been scaled by traditional single function and improved multi-elementary function. The results indicated that more detail on the pinning mechanism in samples, such as the relative pinning strength of each active pinning center, could be given by the multi-elementary scaling

[en] The Ag-sheathed (Bi,Pb)-2223 tapes with different filament number (10, 25 and 30 filaments) and distribution have been prepared by rectangular deformation using a four-roller machine. The filaments in these tapes are distributed in columns. Trapping magnetic fields investigated on the tape surfaces by using a scanning Hall sensor indicated that J_c distributions of the tapes with different filament number along widthwise are different. The transport AC losses in self-field of the tapes measured at 77 K with frequency from 50 to 1000 Hz showed that the loss generation for the tape with higher J_c at edge part was considerably lower than that of tape with higher J_c at center part. In addition, the frequency dependencies of transport AC losses for these tapes exhibit different behaviours

[en] Top-seeded powder melting process (TSPMP) is an effective melting processing technique for the preparation of high J_c bulk YBCO. The remarkable advantage of TSPMP is that it is very convenient to control the size and distribution of 211 particles within bulk YBCO. We observed the microstructure of TSPMP-YBCO sample and the mean size of 211 particles is about 500 nm and well distributed. The thickness of 123 planes is about 2 μm. The density of twins in line is about (1.2-1.6)x10⁴ cm^-1. We fabricated the YBCO bulk sample with dimensions of diameter 30 mmx15 mm in batch by the TSPMP process. The maximum levitation force was measured to be 85 N at 77 K in 0.5 T, by using diameter28 mmx30 mm NdFeB magnet

[en] We report N* masses in the spin-3/2 sector from a highly-improved anisotropic action. States with both positive and negative parity are isolated via a parity projection method. The extent to which spin projection is needed is examined. The gross features of the splittings from the nucleon ground state show a trend consistent with experimental results at the quark masses explored