New development of concept of electronegativity

The concept of electronegativity (EN), which was proposed by Pauling in 1932, is closely related to such properties of molecules as the polarizability, hardness (softness) and charge distribution, and is an important theoretical basis for judging the properties of substances. With the development of new materials and the increase of interdisciplinary cooperation, EN has been a basic atomic parameter which is widely used in the fields of chemistry, physics and materials science. The development of EN has involved three stages, atomic EN, ionic EN and bond EN. The ionic EN, which is the EN values of elements in different valence states by including the chemical environment of atoms, accurately describes various physical and chemical properties of ions and compounds. The bond EN is a bridge linking atomic EN and the properties of materials, which helps us to establish the quantitative correlation between macroscopic properties and microscopic electronic structures of materials. The concepts of ionic EN and bond EN broaden the scope of EN theory, and play important roles in the design of novel materials. This paper presents a detailed introduction of a new development of EN and its applications in materials research. Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-05-0278) and Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 200322)     

Study on the specific interaction between angiogenin and aptamer by atomic force microscopy （AFM）

The specific interaction between angiogenin and aptamer has been investigated by using AFM. The specificity of the interaction is revealed by comparing the binding probability of aptamer to other elements in a series of control experiments. The results have shown that there is specific interaction force between angiogenin and aptamer. Moreover, the single molecular pull-off force between angiogenin and aptamer has also been determined using the Poisson statistical method to be 133.7±11.7 pN. These findings obtained are helpful to the better revelation of recognition mechanism between angiogenin and aptamer, which provided basis for further understanding the inhibition of the aptamer to angiogenic activity.     

Synthesis and characterization of BiFeO3 nanotube arrays and Y-junction BiFeO3 nanotubes

Multiferroic BiFeO₃ (BFO) nanotube arrays (∼100 nm in diameter and ∼50 μm in length) were synthesized by the sol-gel method utilizing the anodic aluminum oxide (AAO) membrane technique. The microstructure and chemical components of the BFO nanotubes were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS). The BFO nanotubes exhibited polycrystalline microstructures. The novel Y-junction BFO nanotubes were simultaneously fabricated. Supported by the National Natural Science Foundation of China (Grant No. 90306010), Program for New Century Excellent Talents in University (Grant No. NCET-04-0653) and National Basic Research Program of China (Grant No. 2007CB616911)     

Theoretic study of the reaction mechanism between （Me）3CO· radical and trans-3-hexene

The reaction mechanism between （Me）3CO· radical and trans-3-hexene in benzene was studied for the first time at the B3LYP/6-311＋＋G（d,p）//B3LYP/6-31G（d）＋ZPVE level. Two distinct elementary channels were identified as： （1） abstraction-addition; （2） addition-addition-elimination. Analysis of the potential energy surface demonstrates that for the title reaction, channels （1） and （2） have the major and minor contribution, respectively. Our calculated results can well explain the recently observed product distribution by Coseri et al. （J. Org. Chem. 2005, 70, 4629）. However, we found that the addition-abstraction channel proposed by Coseri et al. is kinetically infeasible.     

Coexistence of normal, super-, and hyper-deformation in nuclei: A study with angular momentum projection method

Angular-momentum-projected energy surface calculations for A ≈ 110 nuclei indicate three distinct energy minima occurring at different angular-momenta. These correspond to normal, super-, and hy- per-deformed shapes coexisting in one nucleus. 110Pd is studied in detail, with a quantitative prediction on super- and hyper-deformed spectra by the Projected Shell Model calculation. It is found that several other neighboring nuclei in the A-110 mass region, with the neutron number around 64, also exhibit clear s...     

Influence of location-dependent protuberance damage on cell viability

The influence of femtosecond laser-induced damages on viability of olfactory ensheathing cells (OECs) is investigated. Several cytokinetic processes including cellular damage, recovery and death are discussed. Using femtosecond laser with the power of 100 μW and cutting speed of 2 μm/s, we cut the cellular protuberance with smaller diameter twice in different locations, and then observe the viability of the damaged cells. Under the same conditions, the root of protuberance with larger diameter is cut six times to observe changes of cellular shape. Whether the damage is located in the end, middle or root of protuberance with smaller diameter, the cell viability can recover within 3 h. When the damage is located in the root of protuberance with larger diameter, the damaged cell will die in the way of oncosis. Cytokinetic phenomena including intracellular high Ca²⁺ concentration, cellular morphologic change, recovery and oncosis are discussed. Meanwhile, high Ca²⁺ concentration is observed after femtosecond laser surgery. Therefore, femtosecond laser surgery is an important tool for establishing cell damage model and studying cytokinetics. Supported by National High Technology Research & Development Program of China (Grant No. 2006AA04Z307), Author of National Excellent Doctoral Dissertation of PR China (Grant No. 2006039), National Natural Science Foundation of China (Grant No. 50775104), Natural Science Foundation of Jiangsu Province (Grant No. BK2006507) and Jiangsu Provincial Research Innovation Program for College Graduates (Grant No. CX07B_086z)     

Study on elastic modulus of individual ferritin

The mechanical property of individual ferritin was measured with force-volume mapping (FV) under contact mode of atomic force microscopy (AFM) in this work. The elastic modulus of individual ferritin was estimated by the Hertz mode. The estimated value of the elastic modulus of individual ferritin was about 250－800 MPa under a small deformation. In addition, the elastic modulus of individual ferritin was compared with that of the colloid gold nanoparticle.     

Crystallization dynamics of supersaturated NaClO4 aerosols studied by high-speed photography

Single supersaturated NaClO4 aerosol droplets on a quartz substrate were observed by a high-speed video camera for their morphologic changes with decreasing relative humidity （RH）. The supersaturated droplets were found to form anhydrous NaClO4 at -10% RH. Three stages were roughly observed in this process, i.e., the main stem appearance, primary and secondary branches growth, and the deep dehydration. The main stem grew steadily and finished in 120 ms. Affected by both crystal precipitation and water evaporation, primary branches grew for 1200 ms, accompanied by a slower growth of secondary branches. The deep dehydration was more complicated, and lasted for a longer time.     

Effects of temperature on the expression of STN7 and phosphorylation of LHCII proteins in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

In Arabidopsis thaliana, STN7 kinase is required for phosphorylation of LHCII and for state transitions. In this paper, a hydrophilic polypeptide, derived from the amino acid sequence of STN7, was conjugated to a carrier protein, bovine serum albumin （BSA）, to obtain the polyclonal antibody. Immunogenicity and specificity of the polyclonal antibody were evaluated by agar gel immunodiffusion （AGID） test and Western blot analysis. The results show that besides the phosphorylation of LHCII proteins, also the expression of STN7 was regulated by temperature conditions. In addition, the change tendency of LHCII proteins phosphorylation was not only coherent with expression of STN7 with respect to increasing temperature, but also closely related to state transitions. These results would provide useful information for studying regulatory mechanism of LHCII proteins phosphorylation and expression of STN7.     

Effect of the contact distance on transport properties of an orsanic molecular device

Using a spatially symmetric phenyldithiolate molecule sandwiched between two gold electrodes as model system and through shifting one electrode from symmetric contact site to form asymmetric contact, we investigated the properties of electronic transport in such a device by the first-principles. It was found that the/（G ）-V characteristics of a device show significant asymmetry and the magnitudes of current and conductance depend remarkably on the variation of molecule-metal distance at one of the two contacts. Namely, an asymmetric contact would lead to the weak rectifying effects on the current-voltage characteristics of a molecular device. The analysis shows that the HOMO is responsible for the resonant tunneling and its shift due to the charging of the device while the bias voltage is the intrinsic origin of asymmetric/（G）- Vcharacteristics.     

Stable dislocation configuration in the surface layer of metals

The stable dislocation configuration in the surface layer of metals was calculated according to dislo-cation energy theory. It was shown that the stable dislocation configuration was only influenced by Burger's vector, while dislocation line could fluctuate closely around the direction vertical to free sur-face in a limited range.     

Active optical clock

This article presents the principles and techniques of active optical clock, a special laser combining the laser physics of one-atom laser, bad-cavity gas laser, super-cavity stabilized laser and optical atomic clock together. As a simple example, an active optical clock based on thermal strontium atomic beam shows a quantum-limited linewidth of 0.51 Hz, which is insensitive to laser cavity-length noise, and may surpass the recorded narrowest 6.7 Hz of Hg ion optical clock and 1.5 Hz of very recent optical lattice clock. The estimated 0.1 Hz one-second instability and 0.27 Hz uncertainty are limited only by the relativistic Doppler effect, and can be improved by cold atoms. Supported by the National Basic Research Program of China (Grant No. 2005CB724500) and National Natural Science Foundation of China (Grant No. 10874009     

Solvothermal synthesis of CdS nanorods and photovoltaic characteristics of CdS/PVK composite system

Large quantities of CdS nanorods are successfully synthesized through Cd（CH3COO）2·2H2o reacting with Na2S·9H2O and EDA in aqueous solution. XRD result shows that the sample is of hexagonal structure. And TEM result shows that the morphologies of the resulting CdS are mainly in three-armed rod-like structure with a diameter of 10--15 nm and a length of 100 nm. The nanocomposites of CdS/PVK with different molar ratios are prepared by spin coating method on tin-doped indium oxide （ITO） substrate. A notable decrease of photoluminescence （PL） efficiency and a significant enhancement of surface photovoltage signal have been observed in CdS/PVK composites when the molar fraction of CdS increases. We interpret these results as the energy level matching between CdS and PVK in nanocomposites. This energy level matching facilitates fast interfacial charge transfer then increases the separation efficiency of electron-hole pairs and the carrier generation efficiency. The detailed charge transfer process has also been demonstrated.     

Electronic structure and chemical reaction of Ca deposition on resiore8ular poly（3-hexylthiophene） surfaces

Conjugated polymer, regioregular poly（3-hexylthiophene） （rr-P3HT）, films were prepared by spin-coating the rr-P3HT chloroform solution onto clean silicon wafer surfaces. The chemical re- action and electronic structure of Ca deposition on rr-P3HT surfaces were in situ investigated by synchrotron radiation photoemission spectroscopy （SRPES） and X-ray photoemission spectros- copy （XPS）. Upon Ca deposition, Ca-induced band bending of rr-P3HT is observed. In addition, Ca atoms preferentially react with S atoms of rr-P3HT. No obvious reaction between Ca and C atoms can be found. Through the investigation of the evolution of valence band spectra and secondary electron cut-off of rr-P3HT during the process of Ca deposition, an energy level alignment diagram at the Ca/rr-P3HT interface is derived.     

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.     

Enhanced parametric amplification in slow-light photonic crystal waveguides

We demonstrate both theoretically and numerically that slow light can enhance the parametric process of silicon in photonic crystal line-defect waveguides. Specifically, to get the desired gain, the pump power for a given gain medium length or the gain medium length for given pump power can be reduced by （c/vgn）^2 when slow light waveguides are used, where n is the material index of conventional waveguide, vg is the group velocity of the slow light waveguide and c is the light velocity in vacuum.     

Study on cellular internalization of poly（vinyldiaminotriazine）-based hydrogen bonding type non-viral transgene vector

Previously we successfully prepared poly（vinyldiaminotriazine）（PVDT）-based non-viral vectors which complexed piasmid DNA via hydrogen bonding with adenine-thymine base pairs, in this report, surface charges and complex sizes of this system were further examined. The results showed that PVDT-based polymer could cover surface charges of DNA resulting in slightly negative or neutral complexes. It was also found that the complex sizes were governed by two events： the aggregation induced by the instability of neutral particles, and more compact complexes produced by PVDT-based polymers. In the study of cellular uptake, chlorpromazine and filipin III were used to inhibit clathrin-and caveolae-mediated endocytosis, respectively. We found that PVDT-based systems were transported into cells via a non-clathrin, non-caveolae mediated endocytosis. This special process was studied by temperature inhibition and kinetics assays. It was revealed that such a pathway was characterized by （i） a more en- ergy dependent process and （ii） a much slow transfection-effective internalization.     

Crack spacing of unsaturated soils in the critical state

The cracking mechanism of unsaturated soils due to evaporation is poorly understood, and the magnitude of crack spacing is usually hard to estimate. In this work, cracks were postulated to occur succedently rather than simultaneously, that is, secondary cracks appear after primary cracks as evaporation continues. Formulae of the secondary crack spacing and secondary trend crack spacing were then derived after stress analysis. The calculated spacing values were consistent with the published experimental data. Meanwhile, the effect of the Poisson ratio on the crack spacing was analyzed, which showed that the magnitude of crack spacing was proportional to the Poisson ratio in the range of [0.30, 0.35].     

Expanded flux variability analysis on metabolic network of Escherichia coli

Flux balance analysis, based on the mass conservation law in a cellular organism, has been extensively employed to study the interplay between structures and functions of cellular metabolic networks. Consequently, the phenotypes of the metabolism can be well elucidated. In this paper, we introduce the Expanded Flux Variability Analysis （EFVA） to characterize the intrinsic nature of metabolic reactions, such as flexibility, modularity and essentiality, by exploring the trend of the range, the maximum and the minimum flux of reactions. We took the metabolic network of Escherichia coli as an example and analyzed the variability of reaction fluxes under different growth rate constraints. The average variability of all reactions decreases dramatically when the growth rate increases. Consider the noise effect on the metabolic system, we thus argue that the microorganism may practically grow under a suboptimal state. Besides, under the EFVA framework, the reactions are easily to be grouped into catabolic and anabolic groups. And the anabolic groups can be further assigned to specific biomass constitute. We also discovered the growth rate dependent essentiality of reactions.     

Study on high efficient electric discharge milling of silicon carbide ceramic with high resistivity

A new method which employs a group pulse power supply for electric discharge milling of the silicon carbide ceramic with the resistivity of 500 Ω·cm is presented. Due to the good machining stability and high pulse utilization, the material removal rate （MRR） can reach 72.9 mm^3/min. The effects of high-frequency pulse duration, high-frequency pulse interval, peak voltage, peak current, polarity, rotate speed and group frequency on the process performance have been investigated. Also the EDMed surface microstructure is examined with a scanning electron microscope （SEM）, an X-ray diffraction （XRD）, an energy dispersive spectrometer （EDS） and a micro hardness tester. The results show that the conditions of smaller high-frequency pulse duration and pulse interval, higher peak voltage and peak current, and positive tool polarity are suitable for machining the SiC ceramic. The optimal rotate speed is 1090 r/min and the preferable group frequency is 730 Hz. In addition, there is a small quantity of iron on machined surface when machining with steel electrode. The average grain size of the EDMed surface is smaller than that of the unprocessed, and the micro hardness of machined surface is superior to that of the unprocessed.