A new member of the calix[4]crown family:Facile synthesis and characterization of a calix[4]crown-9 cone conformer

25,27-Dipropoxy-p-tert-butylcalix[4]crown-9 cone conformer 5 was readily synthesized via an intramolecular cyclization strategy in good yields.The structures of all the new compounds involved were confirmed by NMR,ESI-MS and elementalanalyses.All of them were proved to be in the cone conformation.     

Hydrophobic surface modification of chitosan gels by stearyl for improving the activity of immobilized lipase

The hydrophobic surface modification of chitosan gels was carried out using the amidating reaction of amido groups on a gel surface with stearic acid activated by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride(EDC) and N-hydroxysuccinimide (NHS).Lipases from Candida rugosa were adsorbed on the nascent chitosan gels(CS) and stearyl-modified gels(SCS) with different degrees of amidation.The increased surface hydrophobicity of chitosan gels improved the adsorption capacity and activity of the ...     

High-resolution photoacoustic microscope for rat brain imaging in vivo

<正>A reflection-mode photoacoustic microscope(PAM) for rat brain imaging in vivo is constructed.A pulsed laser is used as an excitation source,and a focused ultrasound transducer is adopted to collect the photoacoustic signal.Raster scanning is applied to acquire three-dimensional(3D) data.The obtained measurements of the lateral and axial resolutions of the microscope are 45 and 15μm,respectively.The imaging depth in the chicken breast tissue is 3.1 mm at a signal-to-noise ratio(SNR) of 20 dB without any signal averaging.The imaging speed is 30 A-line/s.Experimental results in vivo demonstrate the capability of 3D imaging of the brain vessels of the rat after removing the skull.     

Low birefringence depressed cladding photosensitive fiber

The highly Ge-doped photosensitive fiber （PSF） has been widely used in the fabrication of fiber Bragg gratings （FBGs）. Its birefringence and cladding mode coupling characteristics greatly influence FBG＇s transmission feature in communication application areas. In this work, a new concept of the PSF is introduced which, along with an optimized birefringence design, a precisely controlled fabrication process, and a cladding mode depressed design, results in a written FBG with -25-dB clad mode-depressed ratio and a polarization mode dispersion value less than 0.045 ps.     

Numerical simulations and experimental investigations on transverse effects of two-wave mixing in a photovoltaic photorefractive crystal

The transverse effects of two Gauss waves mixing in a photovoltaic photorefractive crystal,i.e.,the dynamical evolutions of signal beam with different parameters,are traced numerically and experimentally.Both the one-dimensional numerical simulations and two-dimensional experimental investigations show that the self-focusing effect of signal beam becomes more obvious as the intensity of pump beam and the angle between the signal and pump beams increase.In accordance with these results,the state of two Gauss...     

Quasi-variational principles of single flexible body dynamics and their applications

The reasons for studying single flexible body dynamics are that on one hand, it is the basis of flexible multi-body dynamics. If the theory of the single flexible body dynamics has been deeply studied, the theory of flexible multi-body dynamics will be researched easily. On the other hand, it has its unique and important applications. Quasi-variational principle of non-conservative single flexible body dynamics is established under the cross-link of particle rigid body mechanics and deformable body mechanics. Taking the interceptor as an example, this paper has explained the physical meaning of the quasi-stationary value condition of the quasi-variational principle in non-conservative single flexible body dynamics. Taking the launch of rocket as an example, it has illustrated the features of “one force for two effects” in a single flexible body dynamics. With an example of the extending flexible beam coupled with the spacecraft attitude, it has shown the transition from the single flexible body dynamics to the flexible multi-body dynamics. Finally, a number of related problems are discussed. Supported by the National Natural Science Foundation of China (Grant No. 10272034), the Doctoral Education Foundation (Grant No. 20060217020), and the Natural Science Foundation of Harbin Engineering University (Grant No. HEUF04003)     

含裂纹体蠕变断裂理论及其应用研究

评介了蠕变断裂力学研究概况．着重论述含裂纹材料与结构的蠕变断裂、蠕变损伤、蠕变疲劳裂纹扩展和寿命预估等方面研究的近期进展．从中介绍蠕变断裂力学的研究途径、方法及其广阔的工程应用前景      

悬浮体进样石墨炉原子吸收光谱法直接测定煤中微量砷

以Pd为基体改进剂 ,建立了浮体制样石墨炉原子吸收光谱法直接测定煤中微量As的方法。研究了悬浮体的稳定性、试样粒度、基体改进剂、灰化温度、原子化温度和常见共存离子等因素对待测物信号强度的影响。在优化实验条件下 ,方法的检出限为 0 0 5 4 μg·g-1,相对标准偏差 (RSD)为 8 9%     

ADMISSIBILITY IN THE GENERAL GROWTH CURVE MODEL WITH RESPECT TO RESTRICTED PARAMETER SETS UNDER MATRIX LOSS FUNCTION

In this paper, we study the issue of admissibility in the growth curve model with respect to restricted parameter sets under matrix loss function. We obtain some neces- sary and sufficient conditions that the linear estimators of KBL are admissible in the class of homogeneous linear estimators and in the class of non-homogeneous linear estimators under the growth curve model with respect to restricted parameter sets, respectively.     

THE DYNAMICS OF FERTILITY IN C-K MODEL WITH ENDOGENOUS FERTILITY

lhtroduCtlonThe relatloDshlp bet W6W6en the economic gr OWOWth and population growth Is the one of mostimportant problems In the economic growth theorem．In the empirical analyses,the level offertility and the level ofincomeper caplta Is one of*the strongest observably negative correl砒ions,In cross－country dataIS]．Constructing a mathematical model to confirm the empirical indingsIs a m叼or method In thetheoretical study、BeckerI6];GalorI7]and TaTamuraW use OLG modelto discuss this…