An X-ray crystallographic study of the inclusion properties of additionally dimethylated members of the 2′-hydroxy-2,2,4-trimethylflavan host series

Consideration of the shape and hydrogen bonding pattern of anentire guest unit, in the known 2:1:2 complex of 2′-hydroxy-2,4,4,7,4′-pentamethylflavan (1) with 1,4-dioxan and water, has indicated a structurally compatible guest,trans-1,4-bis(hydroxymethyl)cyclohexane (3b) which is selectively clathrated from a mixture with itscis isomer (3a). The new complex is triclinic, space group,P \(\bar 1\) , witha=8.137(1),b=9.106(1),c=14.552(2) Å, α=93.56(1), β=94.08(1), γ=98.62(1)°, and two host and one guest molecule in the unit cell. A novel hydrogen bonded host-guest arrangement has also been found for host (1), involving ethanol and piperazine [triclinic, space groupP \(\bar 1\) , witha=8.438(1),b=10.252(1),c=14.052(1) Å, α=71.28(1), β=89.72(1), γ=83.88(1)δ]; while for the 1:1 ether adduct of (1) the triclinic unit cell, space groupP \(\bar 1\) , is approximately doubled in volume [a=8.309(2),b=10.546(3),c=26.664(6) Å, α=102.10(2), β=100.48(2), γ=81.04(2)°], there now being two crystallographically independent host-guest units involving ?OH·OEt₂ hydrogen bonds of length 2.71(1) Å and 2.77(1)Å. In the 2:1 complex of the isomeric host 2′-hydroxy-2,4,4,6,5′-pentamethylfavan (2) withN, N′-dimethylpiperazine (5) [triclinic space groupP \(\bar 1\) , witha=7.411(1),b=10.143(3),c=15.109(3)Å, α=98.73(2), β=88.30(1), γ=109.72(2)°] the centrosymmetric chair-shaped guest molecule is clamped by two axially oriented ?OH...N hydrogen bonds of length 2.759(3)Å.     

On the Intermittency in Nuclear Fragmentations

A simple Monte Carlo simulation and even a partition method can be used to reproduce quite well the power law behavior between the factorial moment and the charge interval of fragment charge distributions from the multifragmentation of ¹⁹⁷Au nucleus bombarding emulsion at～1 GeV/nucleon. This indicates that the above power law seems not to be a unique precursor of the intermittent behavior in nuclear multifragmentations.     

The measurement of99Tc in seaweed: Results from an international intercomparison exercise

Five samples of brown seaweed, collected from a variety of sites around northern Europe, were distributed to 14 laboratories for analysis of⁹⁹Tc. Consistency in results between laboratories was found to be strongly correlated with concentration levels, with results diverging markedly at⁹⁹Tc concentrations below 100 Bq·kg⁻¹. No systematic differences were apparent between radiometric and mass based techniques but the results do suggest that the use of Re as a tracer may lead to an underestimation of⁹⁹Tc levels.     

EQUATION OF STATE OF HOT NUCLEI BEFORE BREAK-UP

Following the method developed by the authors,recently,the equation of state of hot nuclei(²³⁸U in concrete) before break-up was investigated numerically.The isotherms are drawn in the plan of the general pressure P versus volume V_RT. They are similar to those of Van der Waals gas.The critical temperature of phase transition should correspond to the isotherm with one turning point only.It turns out that the data of mass yield distribution can be reproduced by many pairs of parameters T and V_RT (freeze-out temperature and freeze-out volume) varying in certain range.For each isotherm (each T),the data are always best reproduced by the value of V_RT located at the maximum general pressure within two phases coexistence region.     

相对论性核与乳胶(Ag)碰撞中灰粒子的系统研究 *

用描写相对论性核 核碰撞的LUCIAE模型和相应的事件产生器系统地研究了 1 4.6 ,6 0和 2 0 0AGeV的O核、2 0 0AGeV的Si和S核以及 1 1 .6AGeV的Au核与乳胶 (Ag)碰撞中灰粒子产生的平均多重数、多重数分布以及角分布 3个物理量同入射能量、射弹质量及碰撞中心度间的关系 ,还研究了再散射在灰粒子产生机制中的作用 .LUCIAE的这些研究结果与相应的EMU0 1乳胶实验结果都相一致 .     

A discrete time car following model and the bi-parameter logistic map

A discrete time model for car following behaviour is investigated. It is found that the model can be expressed in the form of a logistic map with multiple control parameter values. The case where the logistic map has a bi-value control parameter is investigated and relevant Feigenbaum diagrams are presented and the behaviour of the Lyapunov exponent is investigated. Divergent behaviour in the chain of vehicles is also considered.     

Energy Dependence of String Fragmentation Function and φ Meson Production

The φ meson productions in Au+Au and/or Pb+Pb collisions at AGS, SPS, RHIC, and LHC energies have been studied systematically with a hadron and string cascade model LUCIAE. After considering the energy dependence of the model parameter α in string fragmentation function and adjusting it to the experimental data of charged multiplicity to a certain extent, the model predictions for φ meson yield, rapidity, and transverse mass distributions are compatible with the experimental data at AGS, SPS and RHIC energies. A calculation for Pb+Pb collisions at LHC energy is given as well. The obtained fractional variable in string fragmentation function shows a saturation in energy dependence. It is discussed that the saturation of fractional variable in string fragmentation function might be a qualitative representation of the energy dependence of nuclear transparency.     

Charged Multiplicity Density and Number of Participant Nucleons in Relativistic Nuclear Collisions

The energy and centrality dependencies of charged particle pseudorapidity density in relativistic nuclearcollisions were studied using a hadron and string cascade model, JPCIAE. Both the relativistic p+p experimental dataand the PHOBOS and PHENIX Au+Au data at RHIC energy could be fairly reproduced within the framework ofJPCIAE model and without retuning the model parameters. The predictions for Pb + Pb collisions at the LHC energywere also given. We computed the participant nucleon distributions using different methods. It was found that thenumber of participant nucleons is not a well defined variable both experimentally and theoretically. Thus it may beinappropriate to use the charged particle pseudorapidity density per participant pair .as a function of the number ofparticipant nucleons for distinguishing various theoretical models.     

相对论重离子碰撞中Λ粒子产生和Λ/p比率

利用强子输运–弦碎裂模型研究了200A GeV重离子碰撞中Λ多重产生和Λ/p比率.研究了它们随反应系统大小和碰撞中心度的变化.研究表明Λ和p多重数都随反应系统增大和随碰撞中心度提高而增大,但它们的比率基本保持不变.Λ的湮没截面大小变化对Λ的多重数产生有一定影响,但对Λ/p比率影响不大.结果很好地再现了pp反应中Λ/p比率.并获得这一比率在AA反应中是pp反应中的3—5倍.     

ALADIN热曲线的微正则系综分析

用微正则瞬时多碎裂统计模型分析了ALADIN热曲线.结果表明落在ALADIN热曲线温度平台(温度扭曲)附近的弹剩余核(热核)的理论代表点,并不落在相应弹剩余核热曲线的温度平台(扭曲)范围内,从而对ALADIN热曲线是否可作为核液气相变的证据提出质疑.