The elasticity of an individual polymer nanoparticle may be greatly different from that of the bulk one. Understanding the properties of individual particles such as elasticity and deformation under external forces is of great importance in controlling the final structures and functions of bulk materials. We study the compression properties of single polyethylenimine （PEI） particles using vibrating scanning polarization force microscopy. By controllably imaging PEI particles at different vibration amplitude set-point values, it is demonstrated that we can compress the single PEI nanoparticle with an atomic force microscopy tip in different loads. Based on the force-height and force-strain curves obtained, Young＇s moduli of PEI （5-160 MPa） in three force regions are estimated according to the Hertz model The results indicate that PEI has excellent elasticity, which may contribute to its high efficiency as vectors in gene transfection.
A Neutron Time-of-Flight(NTOF) spectrometer, based at the Heavy Ion Research Facility in Lanzhou(HIRFL) was developed for studies of neutron production of proton induced spallation reactions related to the ADS project. After the presentation of comparisons between calculated spallation neutron production doubledifferential cross sections and the available experimental data, a detailed description of the NTOF spectrometer is given. Test beam results show that the spectrometer works well and data analysis procedures are established.The comparisons of the test beam neutron spectra with those of GEANT4 simulations are presented.
The unzipping process of double-stranded DNA is analysed using a discrete model at the base level [Chin. Phys. Lett. 22 （2005）1540]. The numerical results are consistent with the experimental observations on the force-displacement behaviour including the sequence-dependence. We find that the hydrogen bond interaction in a base pair is crucially important to the force-displacement profile.
The multiplicity of fragments in Fermi energy heavy-ion collisions was experimen- tally extracted. Compared with the results of calculation using the antisymmetrized molecular dynamics （AMD） model which accounts for the primary fragments only, the results calculated using the AMD together with a statistical decay code GEMINI to account for the deexcitation of excited primary fragments are in better agreement with those extracted from the experiment. This observation indicates that the experimental multiplicity distribution may be significantly different from those of primary fragments.
杨昆曹喜光石福栋刘星泉张苏雅拉吐黄美容王建松陈志强R. WADAS. KOWALSKIT. KEUTGENK. HAGELA. BONASERAJ. B. NATOWITZT. MATERNAL. QINP. K. SAHU
An experimental method was used to evaluate the primary isotope yields of semi-central collisions in the reaction system64Zn+112Sn at 40A MeV.The characteristic nature of the hot nuclear matter at the time of the isotope formation was studied.The multiplicities of light particles(LPs) associated with intermediate mass fragments(IMFs) were determined experimentally by using a kinematical focusing technique.The primary isotope distributions,reconstructed by a Monte Carlo method,were compared with those of the AMD-Gemini simulations.ac/T=0.11 and asym/T=3.34 were extracted from the reconstructed primary fragments yield.These are consistent with those of the primary fragments of the AMD simulation.
LIN WeipingWADA RoyHUANG MeirongLIU XingquanZHAO MinghuiCHEN Zhiqiang
High spin states in ^174Re are investigated via the ^152Sm（^27 AL,5nγ）^174Re reaction and γ - γ coincidence relationships are analysed carefully. A new band is identified due to its spectroscopic connection with the known π1/2^-[541] × ν1/2^-[521] band. This band is proposed to be the ground-state band built on the π1/2^-[541]× ,ν5/2^-[512] configuration in view of the low-lying intrinsic states in the neighbouring odd-mass nuclei. It is of particular interesting that the new band exhibits a phenomenon of low-spin signature inversion, providing a new situation for theoretical investigations.
张玉虎郭松周小红马龙郭文涛Oshima M.Toh Y.Koizumi M.Osa A.Kimura A.Hatsukawa Y.Sugawara M.Kusakari H.
The gamma response function is required for energy calibration of EJ301 （5 cm in diameter and 20 cm in height） organic liquid scintillator detector by means of gamma sources. The GEANT4 and FLUKA Monte Carlo simulation packages were used to simulate the response function of the detector for standard 22Na, 60Co, 137Cs gamma sources. The simulated results showed a good agreement with experimental data by incorporating the energy resolution function to simulation codes. The energy resolution and the position of the maximum Compton electron energy were obtained by comparing measured light output distribution with simulated one. The energy resolution of the detector varied from 21.2% to 12.4% for electrons in the energy region from 0.341 MeV to 1.12 MeV. The accurate position of the maximum Compton electron energy was determined at the position 81% of maximum height of Compton edges distribution. In addition, the relation of the electron energy calibration and the effective neutron detection thresholds were described in detail. The present results indicated that both packages were suited for studying the gamma response function of EJ301 detector.
High spin states in ^174Re have been investigated via the ^152Sm （^27 Al, 5nγ） ^174Re reaction. Gamma-ray excitation functions, x-γ and γ-γ coincidences have been measured. Two rotational bands built on the πh9/2 × vi13/2 and πh11/2 × vi13/2 configurations have been identified and extended up to high-spin states. The relative spin and parity of the band levels have been unambiguously fixed due to observations of several inter-band transitions. Both the bands show the low-spin signature inversion, which is consistent with systematic expectations for the high-j two-quasiparticle bands in the A = 170 mass region.
张玉虎郭松周小红马龙Oshima M.Toh Y.Koizumi M.Osa A.Kimura A.Hatsukawa Y.Sugawara M.Kusakari H.
给出了反对称分子动力学模型(AMD)计算的50 Me V/nucleon112Sn+112Sn反应的分析结果。该研究是反对称分子动力学模型中统计冻结概念的部分研究结果。利用自洽法结合修正的Fisher模型,提取了发射源的温度和密度分别为T=(6.1±0.2)Me V,ρ/ρ0=0.69±0.03。通过与AMD模型计算的系统在时间演化过程中的最大密度比较,得出碎片发射源的密度远小于系统的最大密度。利用自洽法提取的温度和密度与35 Me V/nucleon的40Ca+40Ca反应系统及40 Me V/nucleon的64Zn+112Sn反应系统所提取的温度和密度非常接近。该结果表明反对称分子动力学模型中,系统在中等质量碎片形成时刻处于统计冻结体积。
