稻纵卷叶螟防治指标的研究

关于稻纵卷叶螟的防治指标问题国内外研究较多,但研究结果极不一致,在同一类型水稻上的防治指标相差10倍左右。笔者1982～1985年采取在池子笼罩、田间笼罩内以接不同密度纵卷叶螟幼虫和剪叶模拟等方法,对不同品种不同生育期水稻进行了经济阈值研究;在此基础上,进行了多点大面积示范推广。 材料和方法 1.池栽水稻不同生育期接虫 调整盐粳2号播栽期,使其在二代稻纵卷叶螟二三龄幼虫期具有孕穗、圆秆拔节和蘖三个生育期。

25%甲维·茚虫威水分散粒剂防治2代纵卷叶螟药效试验

进行25%甲维·茚虫威水分散粒剂防治2代纵卷叶螟药效研究,结果表明:其可有效防治水稻纵卷叶螟,最佳用药适期为1龄幼虫高峰期,适宜用量为150 g/hm2,杀虫和保叶效果可达90%以上,适宜推广应用。

Generalized linear joint PP-PS inversion based on two constraints

Conventional joint PP-PS inversion is based on approximations of the Zoeppritz equations and assumes constant VP/VS;therefore,the inversion precision and stability cannot satisfy current exploration requirements.We propose a joint PP-PS inversion method based on the exact Zoeppritz equations that combines Bayesian statistics and generalized linear inversion.A forward model based on the exact Zoeppritz equations is built to minimize the error of the approximations in the large-angle data,the prior distribution of the model parameters is added as a regularization item to decrease the ill-posed nature of the inversion,low-frequency constraints are introduced to stabilize the low-frequency data and improve robustness,and a fast algorithm is used to solve the objective function while minimizing the computational load.The proposed method has superior antinoising properties and well reproduces real data.

The Influence of Edge Restraining Stiffness on the Transverse Vibrations of Rectangular Plate Structures

This paper presents an analytical study on the influence of edge restraining stiffness on the transverse vibrations of rectangular plate structure. An improved Fourier series method was employed to analyze the transverse vibration of plate structure with general elastically restrained boundary conditions. A linear combination of a double Fourier series and eight auxiliary terms was sought as the admissible function of the flexural displacement of the plate, each term being a combination of a polynomial function and a single cosine series expansion. The auxiliary terms were introduced to ensure and improve the smoothness of the original displacement function and its derivatives at the boundaries. Several numerical examples were given to demonstrate the validity and accuracy of the current solution. The influences of translational and rotational stiffness on the natural frequencies and mode shapes of plate were analyzed by numerical results. The results show that the translational stiffness has bigger influence on the natural frequencies than the rotational stiffness. It is generally well known that little change of the rotational stiffness has little influence on the mode shapes of plate. However, the current work shows that a very little change of rotational stiffness value may lead to a large change of the mode shapes of a square plate structure.

Cyclic beamforming using fractional Fourier transform domain cyclostationarity

A minimum mean-squared error （MSE） beamforming algorithm employing the optimum fractional Fourier transform （Opt-FrFT） domain second-order cyclostationarity is proposed. This method can efficiently filter out the compact desired chirp signal, with a consequence that the cyclically uncorrelated interferences and stationary （colored） Gaussian noise are greatly suppressed in the Opt- FrFT domain. This improves the MSE minimization cyclic beamformer by reducing effectively the Opt-FrFY domain signal-noise cross terms in the presence of finite data length de-correlation operation. Simulation results show that the new method works well under a wide range of signal-to-noise ratio （SNR） and signal-to-interference ratio （SIR）.

WAXD and FTIR Studies of Electron Beam Irradiated Biodegradable Polymers

Poly（L-lactic acid） （PLLA） and poly（e-caprolactone） （PCL） have been receiving much attention lately due to their biodegradability in human body as well as in the soil, also due to their biocompatibility, environmentally friendly characteristics and non-toxicity. Morphology of biodegradable polymers affects the rate of their biodegradation. A polymer that has high degree of crystallinity will degrade at a slower rate due to the inherent increased stability. PCL homopolymer crosslinking degree increases with increasing doses of high energy radiation. On the other hand, the irradiation ofPLLA homopolymer promotes mainly chain-scissions at doses below 250 kGy. In the present work, twin screw extruded films of PLLA and PCL biodegradable homopolymers and 50：50 （w：w） blend were electron beam irradiated using electron beam accelerator Dynamitron （E = 1.5 MeV） from Radiation Dynamics, Inc. at doses in the range of 50 kGy to 103 kGy in order to evaluate the effect of electron beam radiation. Wide-angle X-ray diffraction （WAXD） patterns of non irradiated and irradiated samples were obtained using a diffractometer Rigaku Denki Co. Ltd., Multiflex model; and Fourier transform infrared spectroscopy （FTIR） spectra was obtained using a NICOLET 4700, attenuated total reflectance （ATR） technique. By WAXD patterns of as extruded non irradiated and irradiated PLLA it was verified broad diffusion peaks corresponding to amorphous polymer. There was a slight increase of the mean crystallite size of PCL homopolymer with increasing radiation dose. PCL crystalline index （CI） decreased with radiation dose above 500 kGy. But then, PLLA CI increased with radiation dose above 750 kGy. From another point of view, PLLA presence on the 50：50 blend did not interfere on the observed mean crystallite size increase up to 250 kGy. From 500 kGy to 103 kGy the crystallite size of PCL was a little bigger in the blend than the homopolymer. In contrast, FTIR results have shown that this technique was not sensitive enough to observe the degradation promoted by ionizing radiation of the studied homopolymers and blends, and neither on the miscibility of the blends.

Docetaxel-loaded mixed micelles composed of Solutol HS15 and Pluronic F127 or folate-conjugated F127: preparation, optimization and in vitro comparative characterization

In this study, two kinds of docetaxel （DTX）-loaded mixed micelles, composed of Solutol HS15 （HS 15）/Pluronic F127 （F 127） or folate-conjugated F127, （SF-DTX and FSF-DTX）, were prepared by the thin-film hydration method and evaluated in vitro. Both SF-DTX and FSF-DTX were spherical with diameter close to 23 nm. They had high encapsulating efficiency （99.05% and 90.28% for SF-DTX and FSF-DTX, respectively） and sustained-release property. SF and FSF were able to enhance the cellular accumulation of DTX in KBv cells and reduce ATP content in A-549 cells. They also were able to reverse multidrug resistance （MDR）. In vitro cytotoxicity and cellular accumulation of DTX suggested an active targeting of FSF-DTX. It could be concluded from the results that the novel F 127/HS 15 system could serve as a potential nanocarrier with the ability of overcoming MDR, and folate-conjugated F 127/HS 15 might achieve active targeting at the same time.

Enhanced tumor-targeted delivery of anticancer drugs by folic acid-conjugated pH-sensitive polymeric micelles

In order to enhance the targeted delivery of anticancer drugs by polymeric micelles, folic acid(FA), the ligand of folate receptor(FR) over-expressed in the most cancer cells, modified p H-sensitive polymeric micelles were designed and fabricated to encapsulate doxorubicin(DOX) by combination of p H-sensitive amphiphilic polymer poly(2-ethyl-2-oxazoline)-poly(D,L-lactide) with FA-conjugated poly(2-ethyl-2-oxazoline)-poly(D,L-lactide). The prepared micelles were characterized to have about 36 nm in diameter with narrow distribution, well-defined spherical shape observed under TEM and p H-responsive drug release behavior. Moreover, the tumor targeting ability of the FA-modified p H-sensitive polymeric micelles was demonstrated by the cellular uptake, in vitro cytotoxicity to FR-positive KB cells and in vivo real time near-infrared fluorescence imaging in KB tumor-bearing nude mice. The efficient drug delivery by the micelles was ascribed to the synergistic effects of FR-mediated targeting and p H-triggered drug release. In conclusion, the designed FR-targeted p H-sensitive polymeric micelles might be of great potential in tumor targeted delivery of water-insoluble anticancer drugs.

Preparation and anti-MDR tumors study of folate and TPGS dual-modified DSPE-PEG micelles loaded with docetaxel

Multidrug resistance （MDR） operated by P-glycoprotein （P-gp） is one of the major causes in the treatment failure of cancers. In this work, docetaxel-loaded mixed micelles comprised of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy （polyethylene-glycol）2000 （DSPE-PEG2000）, D-α-Tocopherylpolyethylene glycol 1000 succinate （TPGSIooo） and DSPE-PEG2000-folate were developed to overcome MDR and reduce the side effect of docetaxel in cancer therapy. The diameters of micelles ranged from 13 to 26 nm and the encapsulation efficiencies were all above 85%. The influences of DSPE-PEG2000 and TPGSIooo ratios on the micellar characteristics and anti-resistant tumors effects were evaluated. Micelles with high TPGS1000 amount showed an increased cellular uptake and stronger cytotoxicity against MDR KBv cells. Moreover, the micelles modified by targeting ligand of folic acid exhibited better antitumor effect on folate receptor over-expressing KBv cells. The study provides a method for overcoming MDR in cancer therapy.

Turbulent vortex trains in narrow square arrayed rod bundles of a dual-cooled nuclear reactor

The dual-cooled nuclear reactor is currently considered for improving the designs of current/future nuclear reactors. Investigation of the thermal-hydraulic characteristics of the nuclear reactor via experiments is essential for commercializing the dual-cooled nuclear reactor. In this paper, the turbulent flow in square arrayed six-rod bundles in the form of magnified copies of the dual-cooled and current OPR-1000 nuclear reactor is experimentally investigated by means of hot-wire anemometry and smoke-wire generation methods. Vortex trains which do not exist in an ordinary reactor subchannel are presented in the subchannel of the dual-cooled reactor. The vortices are induced by a span-wise velocity gradient. This flow pulsation phenomenon increases the inter-channel mixing of the subchannel. To understand the periodic feature of the pulsation, axial/cross velocities are measured and the periodic characteristic frequencies are obtained by a Fast Fourier Transform (FFT) analysis. The peak frequency that represents the quasi-periodic pulsation of the flow is increased with an increase in the axial velocity while the wavelength of the pulsation remains constant within a tested range of the Reynolds number (9000 51000). The vortex trains are highly synchronized with each other, as confirmed by means of visualization.

Fractional Fourier transform of Lorentz-Gauss vortex beams

An analytical expression for a Lorentz-Gauss vortex beam passing through a fractional Fourier transform (FRFT) system is derived. The influences of the order of the FRFT and the topological charge on the normalized intensity distribution, the phase distribution, and the orbital angular momentum density of a Lorentz-Gauss vortex beam in the FRFT plane are examined. The order of the FRFT controls the beam spot size, the orientation of the beam spot, the spiral direction of the phase distribution, the spatial orientation of the two peaks in the orbital angular momentum density distribution, and the magnitude of the orbital angular momentum density. The increase of the topological charge not only results in the dark-hollow region becoming large, but also brings about detail changes in the beam profile. The spatial orientation of the two peaks in the orbital angular momentum density distribution and the phase distribution also depend on the topological charge.