对粒子物理标准模型的重新审视

 鉴于当前实验研究结果不断地给基本粒子标准模型提出疑难,揭示轻子、夸克存在亚结构的迹象,例如EMC效应预示轻核与重核之间存在差异,pp碰撞单举截面分布在横能E_T>200 GeV时与QCD计算发生较大偏差,发现了反轻子-夸克共振事例,先后发现了夸克的味变中性流和轻子的味变中性流,轻子的"反常量"等等.这些实验迹象都迫使我们有必要及时对基本粒子标准模型进行一番全面、系统的审视.     

Climatological analysis and modeling of the ionospheric global electron content

In this paper, we calculate the ionospheric global electron content （GEC） from the GPS TEC data along the geographic longitude 120°E during the period of 1996-2004, and investigate the relationship between GEC and 10.7 cm solar radio flux F10.7 and its seasonal dependence with partial correlation analysis. Our results show that GEC is closely correlated with solar activity index F10.7 and is also related with annual and semiannual variations. An empirical GEC model driven by those factors is then to examine the influences of different solar activity proxies for the model input. The results suggest that GEC mainly depends on solar activity and the seasonal variations; the latter is also modulated by solar activity. Furthermore, the magnitude of semiannual variation is a little greater than that of annual variation. Our empirical GEC model is proved to be better than the model proposed by Afraimovich et al.     

A new type of longitudinally driven GMI effect of FeCo-based alloy

On investigating the longitudinally driven GMI effect of the DC annealed Fe36Co36Nb4Si4.8B19.2 alloy ribbon, the current density was 3.2×10^7 A/m^2, the GMI effect responds sensitively （the sensitivity is as high as 2440.2%/（A-m^-1）） to weak magnetic field after a 600-second annealing. The experimental result shows that the sensitivity is closely related to annealing current density, driven current frequency and eroded thickness. GMI effect, current annealing, sensitivity, magnetic domain structure     

Combining docking and comparative molecular similarity indices analysis （COMSIA） to predict estrogen activity and probe molecular mechanisms of estrogen activity for estrogen compounds

Estrogen compounds are suspected of disrupting endocrine functions by mimicking natural hormones, and such compounds may pose a serious threat to the health of humans and wildlife. Close attention has been paid to the prediction and molecular mechanisms of estrogen activity for estrogen com- pounds. In this article, estrogen receptor a subtype （ERa） -based comparative molecular similarity indices analysis （COMSIA） was performed on 44 estrogen compounds with structural diversity to find out the structural relationship with the activity and to predict the activity. The model with the significant correlation and the best predictive power （R^2= 0.965, Q^2 LOO： 0.599, R^2 pred ： 0.825） was achieved. The COMSIA and docking results revealed the structural features for estrogen activity and key amino acid residues in binding pocket, and provided an insight into the interaction between the ligands and these amino acid residues.     

Neutrino mass hierarchy and lepton flavor mixing

In the standard model of particle physics there are three species of neutrinos whose masses were originally assumed to be zero. But the discovery of solar and atmospheric neutrino oscillations indicates that neutrinos are massive and lepton flavors are mixed. In this brief review we first give an overview of our current knowledge about the neutrino mass spectrum and lepton flavor mixing angles, and then comment on the seesaw mechanisms which allow us to understand the origin of tiny neutrino masses. We pay particular attention to the nearly tri-bi-maximal neutrino mixing pattern and the Friedberg-Lee symmetry to derive it. A relatively promising possibility of detecting hot and warm neutrino dark matter in the Universe will also be discussed.     

Spatiotemporal characteristics of the energy radiation sources of the three great earthquakes near Sumatra Island in September 2007

Three strong earthquakes with magnitudes of Mw 8.4, Mw 7.9 and Mw 7.0 occurred in the sea west of Sumatra Island on September 12 and 13, 2007. We relocated the epicenters and focal depths of the three events by means of the reversal-time imaging technique using broadband digital seismic data from worldwide stations ranging from 30° to 90°, imaged the spatiotemporal variation of the energy radiation sources by means of the nonplane wave array technique using the broadband digital seismic data from a generalized array made up of 33 stations of the Capital Region Digital Seismograph Network （CRDSN）, and obtained the rupture duration times, extents and rupture velocities. Also, we discussed the correlations between the locations of the energy radiation sources of the three events.     

Well-defined bis（phenolate） lanthanide methoxides as efficient initiators for the polymerization of cyclic carbonate and lactide

Lanthanide methoxides supported by carbon-bridged bis(phenolate) ligands 2,2′-methylene-bis(6-tert- butyl-4-methylphenoxo) (MBMP2-) [(MBMP)Ln( μ-OMe)(THF)2]2 (Ln = Nd (1), Yb (2)) were synthesized in high yields by the protolysis reaction using (C5H5)3Ln(THF) as starting materials, and complex 1 was structurally characterized. The coordination geometry around the center metal can be best described as a distorted octahedron. Complexes 1 and 2 were shown to be efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) and L-lactide. The mechanism of DTC polymerization was explored by the end group analysis of the oligomer.     

Structural dependences of the <Emphasis Type="Italic">η</Emphasis><Superscript>6</Superscript> complexes of 3-amino-9-ethylcarbazole with chromium tricarbonyl fragment on third-order optical nonlinearities

Degenerate four-wave mixing measurements, using the 35 ps pulses at 532 nm, have been employed to investigate the third-order nonlinear optical parameters of two chromium tricarbonyl complexes η6-bonded to 3-amino-9-ethylcarbazole at either the NH2-substituted aryl ring （1） or the unsubstituted ring （2） and their precursor 3-amino-9-ethylcarbazole （AECz）. The second-order hyperpolarizability y of the compounds 1 and 2 were found to be 42.9×10^-31 and 35.9×10^-31 esu, respectively, approximately one order of magnitude greater than AECz. The relation between the molecular structure and second-order hyperpolarizability of the compounds I and 2 was explored in detail based on the three-level model and the density functional theory （DFT） calculation. The theoretical results indicate that the spatial distribution of electron density has the profound role in the third-order nonlinear optical properties.     

Measurement of the Newtonian gravitational constant based on the principle of free fall

The Newtonian gravitational constant (G) is one of the fundamental physical constants. This paper introduces a method to determine the Newtonian gravitational constant based on the principle of free fall, through measuring the change of gravity from the disturbed mass with an FG5/112 absolute gravimeter. This method has good repeatability. The measurement precision can be improved by error control and a large number of experiments. The constant G is obtained by two experiments, and the measured value is (6.6665±0.0554)×10⁻¹¹ m³/(kg·s²). Supported by the National Basic Research Program of China (Grant No. 2003CB716300) and Key Project of the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-125)     

Applying partial correlation method to analyzing the correlation between ionospheric NmF2 and height of isobaric level in the lower atmosphere

On the basis of a multiple linear regression model performed for ionospheric NmF2, partial correlation method is first applied to investigating the relation between NmF2 and h (the height of isobaric level) in the lower atmosphere over Wuhan, China during 1957―2004. The results show that partial correlation method can eliminate the influences of solar and geomagnetic activities as well as the seasonal varia- tion factors and reveal the true correlation between NmF2 and h in the lower atmosphere. A weak posi- tive correlation between NmF2 and h is found in the middle stratosphere. In addition, by comparing the partial correlation coefficients between NmF2 and its influence factors, we find that NmF2 is mainly affected by solar activity and the seasonal variation factors, and weakly affected by geomagnetic ac- tivity, but hardly affected by h in the lower atmosphere. The study suggests that partial correlation method is a helpful tool for investigating the correlation between ionospheric parameter and its influ- ence factors.     

Dead lithium phase investigation of Sn-Zn alloy as anode materials for lithium ion battery

In this work, based on First-principle plane wave pseudo-potential method, we have carried out an in-depth study on the possible dead lithium phase of Sn-Zn alloy as anode materials for lithium ion batteries. Through investigation, we found that the phases Li_xSn₄Zn₄(x = 2, 4, 6, 8) contributed to reversible capacity, while the phases Li_xSn₄Zn_8−(x−4)(x = 4.74, 7.72) led to capacity loss due to high formation energy, namely, they were the dead lithium phases during the charge/discharge process. And we come up with a new idea that stable lithium alloy phase with high lithiation formation energy (dead lithium phase) can also result in high loss of active lithium ion, besides the traditional expression that the formation of solid electrolyte interface film leads to high capacity loss. Supported by the National Natural Science Foundation of China (Grant No. 50771046), Natural Science Foundation of Guangdong Province (Grant No. 05200534), Key Projects of Guangdong Province and Guangzhou City (Grant Nos. 2006A10704003 and 2006Z3-D2031) and China Postdoctoral Science Foundation (Project No. 20080440764)     

Latitudinal shift and tilt of the ring current during magnetic storms

The equatorial ring current (ERC) theory suggested that the distribution of global disturbed horizontal geomagnetic field only depends on the cosine of station’s latitude. However, we always observe a larger ΔH at higher latitude stations than lower ones, implying that the ERC could tilt or/and shift with respect to the equatorial plane during intense storms. In this paper, we analyze 11 intense magnetic storms from 2000 to 2004, and introduce two configurational factors to characterize the topology of storm time ring current. The results show that ERC has occasionally deviated off equatorial plane with both tilt angle δ_t≈13°―25° and latitude shift δ_s≈0°―21.8°. The ground disturbed field distribution should be improved as ΔH_k = ΔH_maxcos(φ_k-δ ), which agree well with the geomagnetic observations.     

An evidence for the strong association of <Emphasis Type="Italic">N</Emphasis>-methyl-2-pyrrolidinone with some organic species in three Chinese bituminous coals

Three Chinese bituminous coals collected from Shenfu, Heidaigou and Feicheng coal fields were respectively extracted with carbon-disulfide/N-methyl-2-pyrrolidinone （CS2/NMP） mixed solvent （volume ratio 1：1） at room temperature followed by distillation of CS2 under ambient pressure and subsequent removal of most of NMP by distillation at 110℃ under reduced pressure to afford mixed solvent-extractable fractions （MSEFs） with small amount of NMP. Acetone-extractable fraction 1 （AEF1） was obtained by extracting each MSEF under ultrasonic irradiation at room temperature and subsequently using a Soxhlet extractor. Direct extraction of each bituminous coal affords acetone-soluble fraction 2 （AEF2）. GC/MS analysis shows that m/z of base or secondary peak in mass spectra of a series of components from each AEF1 is 98, whereas such components were not detected in AEF2. Since m/z of base peak in mass spectrum of NMP itself is 99, the base or secondary peak at m/z 98 should result from loss of α-H from NMP, i.e., NMP is strongly associated with some organic species （OSs） and thereby the components detected with base or secodary peak at m/z 98 in their mass spectra should be associated NMP-OS.     

Effects of ultraviolet radiation B （UV-B） on photosynthesis of natural phytoplankton assemblages in a marine bay in Southern China

Solar ultraviolet radiation B (UVB) is known to have inhibitive effects on phytoplankton photosynthesis. UVB light decreases rapidly with increasing depth in the water column and exerts different degrees of UVB inhibitive effects on phytoplankton photosynthesis. In this study, the objectives were to quantify effects of UVB on phytoplankton photosynthesis and quantum yield, and to examine UVB effects on phytoplankton photosynthesis when light varies. The insitu experiments were conducted in Da Ya Bay, which is a semienclosed area in the subtropical South China. The results showed a significant reduction of photosynthetic rates and quantum yield in the presence of UVB. Maximum photosynthetic rates (Pmax) and maximum quantum yield (Φmax) were 11%-22% and 17%-49% less under solar radiation with UVB than without UVB. A simplified model was developed to describe the UVB biologically effective fluence rate (E*inh) as an exponential decay function of depth. Light-shift experiments, in which water samples from the surface and at depth of 4 m were divided into several subsamples, and each subsamples were then incubated at different depths with and without UVB in the water column, showed that phytoplankton from the deeper water (4 m) had more inhibitive rates by UVB than that from the surface when exposed to the same light condition.     

Relaxor behavior of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics

n the present work, the phase transitions and relaxor behavior of (1−x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-PT, x = 0.2―0.4) ferroelectric ceramics have been investigated by means of X-ray diffraction, di-electric spectroscopy, the P-E hysteresis loop measurements and Raman scattering techniques. Structural analysis revealed that with the increase of PbTiO₃ content, PMN-PT ceramics experienced a gradual phase transition process from rhombohedral to tetragonal. It is usually believed that such kinds of phase transitions resulted in the linear decrease of relaxation degree. Surprisingly, our analy-sis of the dielectric spectra revealed that the indicator of the degree of diffuseness γ reached the maximum value near morphotropic phase boundary (MPB) (x = 0.32), then decreased with the further increase of PbTiO₃ content. The large dielectric relaxor feature near MPB may be attributed to the for-mation of ordered nanodomains, resulting from complex coexisting nanostructures. Further, the P-E hysteresis loop measurements and Raman analysis of the B-site cation order correlated well with the dielectric measurement results. It was found that the hysteresis loop squareness R_sq received the minimum value while the inverse of the value of full wide of half maximum (FWHM) of A_1g mode reached the maximum value at MPB composition, which showed similar trends to γ.     

Quantitative Estimates of Outcrossing Rates in a Natural Population of Caldesia grandis （Alismataceae）

Outcrossing rate in a natural population of Caldesia grandis was estimated by the dominant random amplified polymorphism DNA (RAPD) marker using 10 open-pollinated progeny arrays of 24 individuals. The multilocus outcrossing rate estimated based on all 25 RAPD loci was 0.872 ±0.033 and the single-locus outcrossing rate was 0.795 ±0.032. Multilocus estimates did not differ significantly from the single-locus estimates. The fixation index, F, in the progeny estimated from RAPD data was -0.142 ±0.000. The estimates of multilocus outcrossing rates (t_m) and single-locus outcrossing rates (t_s) obtained from MLDT clearly indicate that outcrossing is predominant in the open-pollinated C. grandis population. An empirical analysis suggests that 15 should be the minimum number of dominant marker loci necessary to achieve robust estimates of t_m.     

Low-field positive and high-field negative magnetoresistances in multiphase Fe-oxide thin films at room temperature

Multiphase Fe-oxide thin films are fabricated on glass substrates by a facing-target sputtering tech- nique. X-ray diffraction and X-ray photoelectron spectroscopy reveal that Fe, Fe3BO4, γ -Fe2BO3B and FeO coexist in the films. High resolution transmission electron microscopy shows the well-defined colum- nar grain structure with the unoxidized Fe as the core and iron-oxide as the shell. The low-field positive and high-field negative magnetoresistances coexist in such a system at room temperature, which can be explained by considering a shell/core model. Nonlinear current-voltage curve and photovoltaic effect further confirm the tunneling-type conduction.     

Experimental and theoretical studies of the reaction between cationic vanadium oxide clusters and acetylene

The time of flight mass spectrometer coupled with a laser ablation/supersonic expansion cluster source and a fast flow reactor was adopted to study the reactivity of cationic vanadium oxide clusters （VinOS,） toward acetylene （C2H2） molecules under gas phase （P, - 1.14 kPa）, under near room temperature （T, - 350 K） conditions. Association products, VmOnC2H2^＋ （m,n = 2,4; 2,6; 3,7-8; 4,9-11; 5,12-13; 6,13-16, and 7,17）, are observed. The oxidation of C2H2 by （V2Os）n^＋ （n = 1 -3） is experimentally identified. The reactivity of （V2O5）n^＋ decreases as n increases. Density functional theory （DFT） calculations were carried out to interpret the reaction mechanisms. The DFT results indicate that a terminal oxygen atom from V2O5^＋ can transfer overall barrierlessly to C2H2 at room temperature, which is in agreement with the experimental observation. Other experimental results such as the observation of V206C2H2^＋ and nonobservation of V2O7,8C2H2^＋ in the experiments are also well interpreted based on the DFT calculations. The reactivity of vanadium oxide clusters toward acetylene and other hydrocarbons may be considered in identifying molecular level mechanisms for related heterogeneous catalysis.     

Electron dynamics in collisionless magnetic reconnection with a PIC simulation

Two-dimensional particle-in-cell (PIC) simulation is used to investigate electron dynamics in collisionless magnetic reconnection, and the proton/electron mass ratio is taken to be m _i /m _e = 256. The results show that the presence of a strong initial guide field will change the direction of the electron flow. The electron density cavities and the parallel electric field can be found in the electron inflow region along the separatrix, and the electron inflow and density cavities only appear in the second and fourth quadrants. What is different from the results with a smaller mass ratio is that new structures appear in the diffusion region near the X line: (1) Narrow regions of density enhancement and density cavities can be found synchronously in this region; and (2) corresponding to the electron density changes near the X line, the strong parallel electric fields are found to occur in the first and third quadrants. These electric fields perhaps play a more important role in acceleration and heating electrons than those fields located in the density cavities. Supported by National Natural Science Foundation of China (Grant No. 40725013) and Open Research Program Foundation of State Key Laboratory for Space Weather, Chinese Academy Sciences