Formation Process of a TiO2 Inverse Opal

Inverse opals of TiO2 with different filling fractions were fabricated by using an opal of polystyrene spheres as a template.Scanning electron microscopy showed the accumulative process of TiO2.The transmission spectra of inverse opals with different filling fractions were measured and the shifts of transmission dip with the filling fraction were observed.Our investigation made the infiltration process clear,and it might be helpful for further improvement of the fabrication of TiO2 inverse opals.     

Statistical interior properties of globular proteins

The character of forming long-range contacts affects the three-dimensional structure of globular proteins deeply. As the different ability to form long-range contacts between 20 types of amino acids and 4 categories of globular proteins, the statistical properties are thoroughly discussed in this paper. Two parameters N_C and N_D are defined to confine the valid residues in detail. The relationship between hydrophobicity scales and valid residue percentage of each amino acid is given in the present work and the linear functions are shown in our statistical results. It is concluded that the hydrophobicity scale defined by chemical derivatives of the amino acids and nonpolar phase of large unilamellar vesicle membranes is the most effective technique to characterise the hydrophobic behavior of amino acid residues. Meanwhile, residue percentage P_i and sequential residue length L_i of a certain protein i are calculated under different conditions. The statistical results show that the average value of P_i as well as L_i of all-α proteins has a minimum among these 4 classes of globular proteins, indicating that all-α proteins are hardly capable of forming long-range contacts one by one along their linear amino acid sequences. All-β proteins have a higher tendency to construct long-range contacts along their primary sequences related to the secondary configurations, i.e. parallel and anti-parallel configurations of β sheets. The investigation of the interior properties of globular proteins give us the connection between the three-dimensional structure and its primary sequence data or secondary configurations, and help us to understand the structure of protein and its folding process well.     

Proteins:From sequence to structure

Protein sequences as special heterogeneous sequences are rare in the amino acid sequence space. The specific sequential order of amino acids of a protein is essential to its 3D structure. On the whole, the correlation between sequence and structure of a protein is not so strong. How well would a protein sequence contain its structural information? How does a sequence determine its native structure? Keeping the globular proteins in mind, we discuss several problems from sequence to structure.     

Preparation of TiO2 Inverse Opal via a Modified Filling Process

By applying polystyrene opals made by a vertical deposition method as the templates, a modified filling method and a well-controlled calcination process, we have successfully obtained a large-area ordered TiO2 inverse opal with a higher vo]ume fraction (14.5%) and a visib]e photonic bandgap. The influences of the fi]]ing process and calcination conditions on the fabrication of the TiO2 inverse opal are investigated.     

DARK MATTER

<正>Revised September 2013 by M.Drees(Bonn University)and G.Gerbier(Saclay,CEA).25.1.Theory25.1.1.Evidence for Dark Matter:The existence of Dark(i.e.,non-luminous and non-absorbing)Matter(DM)is by now well established[1,2].The earliest,and perhaps still most convincing,evidence for DM came from the observation that various luminous objects(stars,gas clouds,globular clusters,or entire galaxies)move faster than one would expect if they only felt the gravitational attraction of other visible objects.An important example is the measurement of galactic rotation curves.     

Orbital Phase Dependence of Globular Cluster＇s Tidal Radii

The orbits for a sample of 45 galactic globular clusters are calculated using positions and spatial velocities based on recent compilations as well as new measurements of their absolute proper motions.The perigalactic positions of each cluster are used to determine their theoretical tidal radii in the given galactic model.The orbital phase dependence between the theoretical and observed tidal radii is evidenced.     

Characteristic of high-organized PS/BPS photonic crystals

B_2O_3-P_2O_5-SiO_2 (BPS) three-dimensional (3D) high-organized polystyrene (PS) opals and inverse opals with large domain were fabricated and characterized.Scanning electron microscope (SEM) shows three or four small"windows",indicating that a very well interconnection between PS spheres of opal.The ultraviolet-visible (UV-vis) spectra indicate that the photonic band gaps (PBGs) are about 710 and 604 nm for 320-and 270-nm spheres respectively.While according to Bragg's equation,the simulation results should be 762 and 643 nm,which mean that 52 and 39 nm were shifted to blue region,respectively.     

Residual occurrence and energy property of proteins in HNP model

Four categories of globular proteins, including all-α, all-β, α + β, and α /β types, are simplified as the off-lattice HNP model involving the secondary-structural information of each protein. The propensity of three types of residues,i.e., H, N, and P to form a secondary structure is investigated based on 146 protein samples. We find that P residues are easy to form α-helices, whereas H residues have a higher tendency to construct β-sheets. The statistical analysis also indicates that the occurrence of P residues is invariably higher than that of H residues, which is independent of protein category. Changes in bond- and non-bonded potential energies of all protein samples under a wide temperature range are presented by coarse-grained molecular dynamics(MD) simulation. The simulation results clearly show a linear relationship between the bond-stretching/bending potential energy and the reduced temperature. The bond-torsional and non-bonded potential energies show distinct transitions with temperature. The bond-torsional energy increases to the maximum and then decreases with the increase of temperature, which is opposite to the change in non-bonded potential energy. The transition temperature of non-bonded potential energy is independent of the protein category, while that of bond-torsional energy is closely related to the protein secondary structure, i.e., α-helix or β-sheet. The quantitatively bonded- and semiquantitatively non-bonded potential energy of 24 α + β and 23 α /β protein samples are successfully predicted according to the statistical results obtained from MD simulations.     

Face—Centred—Cubic Artificial Opal Embedded with CdS Quantum Dots

Highly monodispersed colloidal silica spheres in sub-micrometra size with distribution standard deviation less than 5% were synthesized by a chemical method.Using the self-crystallization of the silica spheres,we successfully obtained the three-dimensional close-packed face-centred-cubic silica matrices and artificial opals.Then,a colloidal photonic crystal embedded with CdS quantum dots (QDs) was also chemically prepared by using artificial opals as a template.A reflection spectra study reveals that both artificial opals with and without CdS QDs possess (111) directional photonic bandgap features.     

Measurements of aerosol distribution by an elastic-backscatter lidar in summer 2008 in Beijing

Elastic lidar observations of profiles of the aerosol extinction, backscattering coefficients, and the lidar ratio have been performed in Beijing. The elastic lidar transmitts wavelengths of 532 and 355 nm. The measurement altitude can reach up to 6 km. The similarity of the extinction and baekscattering profiles suggests a close relation between the mean transmission and reflection properties. The lidar ratio on July 22, 2008 varied from 10 to 30 sr with the mean value of 20 sr. The profiles of the aerosol properties indicate the cirrus at 6 km altitude and a well-mixed boundary layer from July 22 to 24, 2008. The detected boundary layer also agrees well with the high and stable ozone concentration obtained from the differential optical absorption spectroscopy （DOAS） system.     

Optics of globular photonic crystals

Recent experimental and theoretical results on the optical properties of globular photonic crystals coauthored by the author are presented. The dispersion relation for electromagnetic waves in a 1D photonic crystal that simulates the properties of a selected direction in the globular photonic crystal is calculated. The spectral ranges that are characterized by the anomalous slowing of electromagnetic waves in the photonic crystal and correspond to the stop-band edges are determined. A method for the measurement of the transmission and reflection spectra of the broadband radiation in photonic crystals is proposed. The method enables one to find the characteristics of the stop bands. The features of the secondary emission that emerges in opals due to the UV and visible excitation are reported. The conditions for the low-threshold lasing in opals filled with rareearth elements are presented. The experimental results on the induced-globular light scattering are demonstrated. Such a scattering implies the coherent excitation of vibrational states of the globules in a globular photonic crystal. A new phenomenon (slow light scattering) which involves the excitation of slow photons (slowtons) that correspond to the stop-band edges of the photonic crystal is observed. The conditions for the measurement of the slow light scattering in opals excited using the ruby and nitrogen lasers are experimentally determined. The experimental and theoretical results open up the prospects for low-threshold nonlinear optical processes in material media.     

Spectroscopy of stop bands of globular photonic crystals filled with water

Reflectance spectra from the surface of artificial opals are measured at various globule diameters. A method for calculating the spectra of globular photonic crystals taking into account the globule size dispersion is proposed. The effect of the filling of opal with water on the spectral position of stop bands is revealed. Satisfactory agreement of theoretical results with experimental data was found.     

Optical properties of 3D photonic crystals filled with CdSe/CdS quantum dots

We study 3D globular photonic crystals based on synthetic opals filled with semiconductor core/shell quantum dots CdSe/CdS by measuring the photoluminescence spectra. The spectra were obtained using 369, 384, and 408 nm LED light excitation and involving a pulse YAG laser operating at 365 and 266 nm. The study shows that the photoluminescence spectra of opal filled with CdSe/CdS changes sufficiently in comparison with spectra taken for pure opal and a reference colloidal solution of CdSe/Cds quantum dots in toluene. Such opals may be used to fabricate a narrow-band light sources.     

Dispersion relation of acoustic waves in phononic crystals filled with dielectric or metal

The results of the theoretical study of acoustic properties of globular phononic crystals based on artificial opals consisting of closely packed SiO₂ globules ∼200 nm in diameter are presented. Dispersion characteristics of the samples under study were calculated, the group velocity and effective mass of phonons were determined.     

Localization and Amplification of the Electromagnetic Field in a Globular Photonic Crystal

Using the wave equation, the electromagnetic field distribution is calculated in a globular photonic crystal on the basis of artificial opal in the [111] direction. The electromagnetic field is found to be localized at the edge of the photonic band gap in the first surface pore of the sample. The effect of pumping on a sample is estimated as well. The results open up prospects for the application of artificial opals to solve photon and gravitational conversion problems.     

Acoustic properties of globular photonic crystals based on synthetic opals

Acoustic properties of globular photonic crystals based on synthetic opals and composed of closely packed SiO₂ globules about 200 nm in diameter are theoretically investigated. Dispersion characteristics of the investigated samples are numerically simulated, and the group velocity of acoustic waves and the effective mass of acoustic phonons are found. It is shown that phononic bandgaps in these photonic crystals are within the gigahertz frequency range. The effective mass of the acoustic phonons corresponding to the edges of the bandgaps is found, and a possibility that bound states of acoustic phonon pairs, biphonons, manifest themselves in the light scattering spectra is discussed.     

圆柱形蛋白石和反蛋白石结构光子晶体的制备及其光学性质

研究了在圆柱曲面基底上自组装空心和实心的圆柱形蛋白石和反蛋白石结构光子晶体的方法. 用垂直沉积法在不同曲率半径的毛细管内自组装了空心圆柱形聚苯乙烯(PS)蛋白石结构光子晶体薄膜和二氧化硅 (SiO₂) 反蛋白石结构薄膜; 用类重力沉积法制得实心圆柱形蛋白石和反蛋白石结构光子晶体, 并讨论了这一生长方式中的状态变化过程及影响因素. 用扫描电子显微镜对样品内部结构进行了表征, 用光谱仪测试了光子晶体薄膜的反射光谱, 结果表明: 基底曲率半径和微球粒径的大小是影响空心蛋白石和反蛋白石薄膜质量的主要因素; 微球大小是影响实心结构有序性的主要因素. 关键词： 反蛋白石 空心圆柱 溶胶凝胶协同自组装     

Determination of the real structure of artificial and natural opals on the basis of three-dimensional reconstructions of reciprocal space

The distribution of the scattering intensity in the reciprocal space for natural and artificial opals has been reconstructed from a set of small-angle X-ray diffraction patterns. The resulting three-dimensional intensity maps are used to analyze the defect structure of opals. The structure of artificial opals can be satisfactorily described in the Wilson probability model with the prevalence of layers in the fcc environment. The diffraction patterns observed for a natural opal confirm the presence of sufficiently long unequally occupied fcc domains.     

Temperature dependences of the order parameter for sodium nitrite embedded into porous glasses and opals

The temperature dependences of the order parameter η(T) for sodium nitrite NaNO₂ embedded in porous glasses with average pore diameters of 320 and 20 nm, as well as in artificial opals, have been investigated. It has been demonstrated that the dependence η(T) for sodium nitrite in the porous glass almost coincides with that for the bulk material, whereas this dependence for NaNO₂ in opals differs substantially from that observed in the bulk material and from those previously determined for sodium nitrite in porous glasses with average pore diameters of 3 and 7 nm. It has been revealed that the dependence of the order parameter for sodium nitrite in opals exhibits a temperature hysteresis (approximately equal to 8 K). The temperature dependence η(T) has been described using a simple model, which takes into account the nanopore diameter distribution existing in artificial opals.     

Optical characterization of natural and synthetic opals by Bragg reflection spectroscopy

The Bragg reflection of light from natural and synthetic opals was studied experimentally, and the samples were characterized by atomic-force microscopy. The reflection spectra were theoretically calculated within the model of a planar, periodically layered medium. A comparison of the experimental and calculated data made it possible to determine the parameters of the crystal structure of synthetic opals (lattice constants and sintering coefficients of a-SiO₂ particles). It was concluded that the pores in the structure of natural opals are filled by a material with a refractive index close to that of a-SiO₂.