Evidence for a doubly magic O

The decay energy spectrum for neutron unbound states in ²⁴O (Z=8$Z=8$, N=16$N=16$) has been observed for the first time. The resonance energy of the lowest lying state, interpreted as the ²⁺$2^{+}$ level, has been observed at a decay energy above 600 keV. The resulting excitation energy of the ²⁺$2^{+}$ level above 4.7 MeV, supplies strong evidence that ²⁴O is a doubly magic nucleus. The data is also consistent with the presence of a second excited state around 5.33 MeV which can be interpreted as the ¹⁺$1^{+}$ level.     

Anomalous scaling in epitaxial growth on vicinal surfaces: meandering and mounding instabilities in a linear growth equation with spatiotemporally correlated noise

We have undertaken an extensive analytical and kinetic Monte Carlo study of the (2+1) dimensional discrete growth model on a vicinal surface. A non-local, phenomenological continuum equation describing surface growth in unstable systems with anomalous scaling is presented. The roughness produced by unstable growth is first studied considering various effects in surface diffusion processes (corresponding to temperature, flux, diffusion anisotropy). We found that the thermally activated roughness is well-described by a generalized Lai–Das Sarma–Villain model with non linear growth continuum equation and uncorrelated noise. The corresponding critical exponents are computed analytically for the first time and show a continuous variation in agreement with simulation results of a solid-on-solid model. However, the roughness related to the meandering instability is found, unexpectedly, to be well described by a linear continuum equation with spatiotemporally correlated noise.     

高效液相色谱法测定水体中的氯虫酰胺残留量

采用Kromasil C18不锈钢柱(250mm×4.6mm i.d..5μm),以甲醇-水混合溶剂(65:35,V/V)为流动相,流速1.0mL/min,光电二极管阵列检测器,检测波长236nm和柱温35C,建立了不同水体中氯虫酰胺残留的高效液相色谱分析方法.氯虫酰胺水样直接用二氯甲烷进行液-液分配萃取.在0.10-10mg/L的浓度范围内,氯虫酰胺峰面积(y)与质量浓度(x)呈现良好的相关性,其线性回归方程为y=2170.4x 2641.7,r2=0.9991.井水和池塘水中添加质量浓度为0.01-1.00mg/L时,其平均回收率分别为94.70%-100.37%和89.14%-100.22%,变异系数分别为0.81%-5.11%和1.81%-5.30%,水样中的氯虫酰胺最低检测质量浓度(LOQ)为7.5×10-3mg/L,方法快速、灵敏度高、重现性好,具有较好的准确度和精密度,可用于环境中水样和土壤样中氯虫酰胺的残留检测分析.     

Markoff triples and quasifuchsian groups

We study the global behaviour of trees of Markoff triples overthe complex numbers. We relate this to the space of type-preservingrepresentations of the punctured torus group into SL(2,C). Inparticular, we explore which Markoff triples correspond to quasifuchsianrepresentations. We derive a variation of McShane's identityfor quasifuchsian groups. In the case of non-discrete representations,we attempt to relate the asymptotic behaviour of Markoff triplesto the realisability of laminations in hyperbolic 3-space. Wealso consider how some of these issues might be related formore general surfaces. 1991 Mathematics Subject Classification:57M50.