A new photopolymerizable holographic recording material based on acrylamide and N-hydroxymethyl acrylamide

new polyvinylalcohol-based photopolymeric holographic recording material has been developed. The recording is obtained by the copolymerization of acrylamide and N-hydroxymethyl acrylamide. Diffraction efficiencies near 50% are obtained with energetic exposure of 80mJ/cm². N-hydroxymethyl acrylamide can improve the optical quality of the film. With the increase of the concentration of N-hydroxymethyl acrylamide, the flatness of the film increases, scattering reduces and the straight image is clearer with a small distortion. The postexposure effect on the grating is also studied. The diffraction efficiency of grating increases further during postexposure, gradient of monomer exists after exposure.     

Resisting shrinkage properties of volume holograms recorded in TiO_2 nanoparticle-dispersed acrylamide-based photopolymer

A novel organic–inorganic nanoparticle–photopolymer composite system is developed, and its fundamental holographic recording characteristics are studied. In this hydrophilic TiO2-nanoparticle-dispersed acrylamide photopolymer composite system, the counter-diffusion of monomers and nanoparticles plays a fundamental and key role in hologram grating formation. The experimental results indicate that the volume shrinkage of the nanoparticle–photopolymer film during the holographic recording can be drastically reduced compared with the undoped photopolymer film. It is also found that the diffraction efficiency of the grating recorded in the nanoparticle–photopolymer film depends strongly on the concentration of the TiO2-nanoparticles, and there exists an optimal TiO2-nanoparticle-doping concentration to make the diffraction efficiency and the refractive index modulation reach their maxima. Additionally, the digital data page is stored and reconstructed in the nanoparticle–photopolymer film.     

FeP(Im)−AB bonding energies evaluated with a large number of density functionals (P = porphine,Im = imidazole,AB = CO,NO, and O2)

Sixty-four density functionals, ranging from GGA, meta-GGA, hybrid GGA to hybrid meta-GGA, were tested to evaluate the FeP(Im)–AB bonding energies (E _bond) in the heme model complexes FeP(Im)(AB) (P?=?porphine, Im?=?imidazole, AB?=?CO, NO, and O₂). The results indicate that an accurate prediction of E _bond for the various ligands to heme is difficult with the DFT methods; usually, a functional successful for one system does not perform equally well for other system(s). Relatively satisfactory results for the various FeP(Im)–AB bonding energies are obtained with the meta-GGA functionals BLAP3 and Bmτ1; they yield E _bond values of ca. 1.1, 1.2, and 0.4?eV for AB?=?CO, NO, and O₂, respectively, which are in reasonable agreement with experimental data (0.78–0.85?eV for CO, 0.99?eV for NO, and 0.44???0.53?eV for O₂). The other functionals show more or less deficiency for one or two of the systems. The performances of the various functionals in describing the spin-state energetics of the five-coordinate FeP(Im) complex were also examined.     

新型绿光敏感光致聚合物高密度全息存储特性

用实验方法研究了一种新合成的绿光敏感光致聚合物的高密度全息存储性质.结果表明该种光致聚合物具有较高的衍射效率、大的动态范围和折射率调制度,适合做高密度数字全息存储的记录材料,但材料的灵敏度需要提高,同时读出过程必须考虑曝光过程所导致的布拉格偏移;利用角度复用技术在样品的同一位置记录了20个数字化数据信息页,存储密度达到0.125GBcm3,平均误码率达到5.15×10 关键词： 光致聚合物 高密度数字全息存储 布拉格偏移     

Predicting partition coefficients for isomeric diastereoisomers of some tripeptide analogs

The octanol-water partition coefficients (Log P) of tripeptide diastereoisomers have been calculated by our recently developed method for predicting Log P from the results of AM1 semiempirical calculations. This method can distinguish different diastereoisomers. The differences arise from variations in molecular conformation, which lead to significant differences in the dipole moment and ovality of the different diastereoisomers.     

An ab initio theoretical study of the stereoisomers of tetrahydrocannabinols

An extensive theoretical study of the stereoisomers of tetrahydrocannabinols has been performed at the ab initio HF/6-31G^* and B3LYP/6-31G^* levels. Effects of solvation were calculated with the Onsager model (with full geometry optimization), SCRF with Tomasi's PCM, and isodensity polarization continuum models. Single-point MP2//HF/6-31G^* calculations were carried out. Frequency calculations for all the isomers at the HF/6-31G^* level and for two natural isomers ¹-THC-RR and ⁶-THC-RR at the B3LYP/6-31G^* level were performed. Our results support the findings of the previous AM1 studies that the orientation of the carbocyclic ring and its C1 substituent with respect to the phenyl group hydroxyl oxygen play the major role in the activity. The calculated values of the LUMO energy (lowest unoccupied molecular orbital) and the hardness of the stereoisomers show that for the trans isomers it is easier to remove one electron from its HOMO (highest occupied molecular orbital) to the LUMO and easier to accept an electron from the receptor binding site than for the cis isomers. Combining geometric features (the orientation of the carbocyclic ring and its C1 substituent with respect to the phenyl group hydroxyl oxygen) with electronic features (LUMO and hardness), we explain the activity differences among the stereoisomers.     

Effects of peripheral substituents and axial ligands on the electronic structure and properties of cobalt porphyrins

The effects of peripheral substituents and axial ligands (L) on the electronic structure and properties of cobalt tetraphenylporphyrin (CoTPP) have been studied using DFT methods. Various density functionals were tested, and the ground state of each system was determined by considering several possible low-lying states. The ground states of the fully fluorinated CoTPPF28(L)2 complexes with L = THF, Py, and Im were identified to be high-spin (4E(g)) by the meta-GGA functional tau-HCTH, which contains the kinetic energy density tau, in agreement with experimental measurements. All the pure GGA functionals, including the recently developed mPBE, OPBE, and HCTH/407, show more or less overestimation of the relative energies of the high-spin states. The energy gap between the 2A(1g) and 4E(g) states is insignificant (approximately 0.1 eV) and varies in the order L = Py < L = THF < L = Im. The results and their trend are consistent with 19F NMR studies which show partial population of the 4E(g) state in CoTPPF28(THF)2 and CoTPPF28(Py)2 and a complete conversion to the high-spin state in CoTPPF28(1-MeIm)2. Upon coordination by two very strong field axial CO ligands, CoTPPF28(CO)2 becomes low-spin, as in unligated CoTPPF(x). The influence of the peripheral substituents and axial ligands on the ionization potentials, electron affinities, and CoTPPF(x)-(L)2 binding strength was also investigated in detail.     

Cardiovascular Disease and Possible Ways in Which Lycopene Acts as an Efficient Cardio-Protectant against Different Cardiovascular Risk Factors

Foods rich in antioxidants such as lycopene have a major role in maintaining cardiac health. Lycopene, 80% of which can be obtained by consuming a common vegetable such as tomato, can prevent the disturbances that contribute to cardiovascular disease (CVD). The present work begins with a brief introduction to CVD and lycopene and its various properties such as bioavailability, pharmacokinetics, etc. In this review, the potential cardio-protective effects of lycopene that reduce the progression of CVD and thrombotic complications are detailed. Further, the protective effects of lycopene including in vitro, in vivo and clinical trials conducted on lycopene for CVD protective effects are explained. Finally, the controversial aspect of lycopene as a protective agent against CVD and toxicity are also mentioned.     

番红花红T光敏感光致聚合物全息存储材料

制备了一种以番红花红T为光敏剂的新型全息存储材料,主要用Ar⁺激光器的514.5nm波长的绿光研究材料的全息特性.研究表明,该材料具有较高的衍射效率、曝光灵敏度和较大的折射率调制度,衍射效率近40%,灵敏度为7.22×10^-4cm²/mJ,折射率调制度为3.65×10^-4,同时,在读出时必须考虑布拉格偏移对全息存储的影响.在介质膜中存储了全息图像,再现图像较为清晰,说明该材料适合用作高密度全息存储介质. 关键词： 全息存储 光致聚合物 衍射效率 布拉格偏移     

负热膨胀材料研究进展

本文介绍了负热膨胀材料的制备技术、结构、性能、应用及热缩机理研究的主要进展。分析了负热膨胀材料合成及其应用中存在的主要问题,讨论了刚性单元模模型及其局限性,给出了热缩机理理论和实验特别是第一性原理声子谱计算和拉曼光谱研究的最新进展、存在问题及发展趋势。指出了负热膨胀材料研究中应重点解决的一些重要问题。