微波消解-电感耦合等离子体-原子发射光谱法测定油墨中的铅、铬和钡

建立了微波消解-电感耦合等离子体-原子发射光谱法(ICP-AES)测定油墨中铅、钡和铬元素的分析方法.实验选用钇作为内标物,以减少背景干扰.结果表明,各元素校准曲线的相关系数均为0.9999,样品相对标准偏差小于5％,加标回收率在96.7％-98.8％之间.实验具有较好的精密度和准确性,适合油墨中铅,铬,钡元素的分析.     

污泥中重金属的形态分析及其可浸出性

以自来水厂和污水处理厂的污泥为研究对象,采用Tessier五步法和火焰原子吸收光谱法研究污泥中重金属（Zn、Cu、Cd、Ni、Mn）含量、形态分布以及可浸出性。结果发现,在自来水厂污泥和污水处理厂污泥中重金属总量大小依次为Zn〉Mn〉Ni〉Cu〉Cd,Zn〉Mn〉Cu〉Ni〉Cd,污泥中Zn含量最高,为448.17mg.kg-1;Cd含量最低,为27.17mg.kg-1,超过国家标准,限制了污泥的农用。Tessier形态分析结果表明,污泥中Zn、Cu、Cd主要以稳定态存在;Mn主要以有效态存在,潜在的迁移性和植物毒性最值得关注;Cu浸出率最高,为14.8%,Zn浸出率最低,为0.11%,因此浸出率不仅与金属和污泥的特性有关,而且金属在污泥中赋存的化学形态对其可浸出性也有重要的影响。     

Heavy particle modes and signature of the I-Regime

The recently discovered properties of the I-confinement Regime are explained as resulting from the excitation of a heavy particle mode. The theoretically predicted mode phase velocity in the direction of the electron diamagnetic velocity and the induced confinement of impurities at the edge of the plasma column have been confirmed by the experiments. The direction of the mode phase velocity is consistent with that (opposite) of the spontaneous rotation in the plasma core. The mode is of the “ion-mixing” type, in that it does not produce any electron transport across the fields and it involves significant poloidal magnetic field fluctuations.     

Isospin splittings of doubly heavy baryons

The SELEX Collaboration has reported a very large isospin splitting of doubly charmed baryons. We show that this effect would imply that the doubly charmed baryons are very compact. One intriguing possibility is that such baryons have a linear geometry Q–q–Q$Q\text{–}q\text{–}Q$ where the light quark q oscillates between the two heavy quarks Q  , analogous to a linear molecule such as carbon dioxide. However, using conventional arguments, the size of a heavy-light hadron is expected to be around 0.5 fm, much larger than the size needed to explain the observed large isospin splitting. Assuming the distance between two heavy quarks is much smaller than that between the light quark and a heavy one, the doubly heavy baryons are related to the heavy mesons via heavy quark–diquark symmetry. Based on this symmetry, we predict the isospin splittings for doubly heavy baryons including Ξ_cc${\Xi }_{cc}$, Ξ_bb${\Xi }_{bb}$ and Ξ_bc${\Xi }_{bc}$. The prediction for the Ξ_cc${\Xi }_{cc}$ is much smaller than the SELEX value. On the other hand, the Ξ_bb${\Xi }_{bb}$ baryons are predicted to have an isospin splitting as large as (6.3±1.7) MeV$(6.3\pm 1.7)\text{MeV}$. An experimental study of doubly bottomed baryons is therefore very important to better understand the structure of baryons with heavy quarks.     

On the nuclear modification factor at RHIC and LHC

We show that pQCD factorization incorporated with pre-hadronization energy-loss effect naturally leads to flatness of the nuclear modification factor RAA$R_{\mathit{AA}}$ for produced hadrons at high transverse momentum pT$p_T$. We consider two possible scenarios for the pre-hadronization: In scenario 1, the produced gluon propagates through dense QCD medium and loses energy. In scenario 2, all gluons first decay to quark–antiquark pairs and then each pair loses energy as propagating through the medium. We show that the estimates of the energy-loss in these two different models lead to very close values and is able to explain the suppression of high-pT$p_T$ hadrons in nucleus–nucleus collisions at RHIC. We show that the onset of the flatness of RAA$R_{\mathit{AA}}$ for the produced hadron in central collisions at midrapidity is about pT≈15$p_T\approx 15$ and 25 GeV at RHIC and the LHC energies, respectively. We show that the smallness (RAA<0.5$R_{\mathit{AA}}<0.5$ ) and the high-pT$p_T$ flatness of RAA$R_{\mathit{AA}}$ obtained from the kT$k_T$ factorization supplemented with the Balitsky–Kovchegov (BK) equation is rather generic and it does not strongly depend on the details of the BK solutions. We show that energy-loss effect reduces the nuclear modification factor obtained from the kT$k_T$ factorization about 30–50% at moderate pT$p_T$.     

A systematic study of the fission and evaporation residue excitation functions in complete fusion reactions with weakly bound stable nuclei

We carry out a systematic study on the fusion-fission and evaporation residue excitation functions for the reactions of ^6,7Li, ⁹Be, ^10,11B + ²⁰⁹Bi and ^6,9Li, ⁹Be + ²⁰⁸Pb, in which the projectiles are loosely bound and have low threshold energies against breakup. The fusion cross sections are calculated by the coupled-channel model. The compound nuclei decay are analyzed with the standard statistical model. The fission and evaporation residue excitation functions are well reproduced by our calculations, proving the validity of the standard statistical model in describing the compound nuclei decay in these characteristic reactions. For the compound nuclei with A=215-220 and Z=86-88, the liquid drop fission barriers need to be scaled by 0.80-1.02 to reproduce the experimental data. And a decreasing trend of the scaling factor with increasing fissionability parameter Z²/(50A) is found.     

On the origin of bursts and heavy tails in animal dynamics

Over recent years there has been an accumulation of evidence that many animal behaviours are characterised by common scale-invariant patterns of switching between two contrasting activities over a period of time. This is evidenced in mammalian wake-sleep patterns, in the intermittent stop-start locomotion of Drosophila fruit flies, and in the Lévy walk movement patterns of a diverse range of animals in which straight-line movements are punctuated by occasional turns. Here it is shown that these dynamics can be modelled by a stochastic variant of Barabási’s model [A.-L. Barabási, The origin of bursts and heavy tails in human dynamics, Nature 435 (2005) 207-211] for bursts and heavy tails in human dynamics. The new model captures a tension between two competing and conflicting activities. The durations of one type of activity are distributed according to an inverse-square power-law, mirroring the ubiquity of inverse-square power-law scaling seen in empirical data. The durations of the second type of activity follow exponential distributions with characteristic timescales that depend on species and metabolic rates. This again is a common feature of animal behaviour. Bursty human dynamics, on the other hand, are characterised by power-law distributions with scaling exponents close to −1 and −3/2.