Design of adaptive spatial filter at uniform standard for automatic analysis of digital holographic microscopy

The spatial filtering method is a useful technique for the dynamic and automatic analysis in digital holographic microscopy. It has been shown that the proper selection of the spatial filter would improve the quality of the reconstructed image. However different results would be obtained by employing the spatial filter with different parameter threshold decided at different standard. This paper, according to the histogram analysis of the distribution of the +1 term spectrum of each hologram, gropes for the uniform standard for the decision of the threshold of the adaptive filter. It helps the adaptive spatial filtering method to be more advantageous for the dynamic and automatic analysis.     

The study of ultrafast magnetization dynamics induced by femtosecond laser pulses in GdFeCo amorphous film

The time-resolved magneto-optical Kerr spectroscopy technique is used to study the ultrafast magnetization dynamics induced by femtosecond laser pulses in GdFeCo amorphous film. We study concretely the influence of the different pump fluence and the different external magnetic field on magnetization dynamics of ultrafast demagnetization, magnetization reversal and magnetization recovery. The pump fluence dependence magnetization dynamics shows that the degree of demagnetization, the degree of magnetization reversal and the time of magnetization recovery increase with pump fluence, which can be interpreted by the “three-temperature” model. The external magnetic field dependence magnetization dynamics shows that the rate of magnetization reversal increases with the external field, which accord with the magnetization reversal mechanism based on the reversed magnetic domain nucleation and domain-wall motion.     

Facile synthesis of ordered magnetic mesoporous gamma-Fe2O3/SiO2 nanocomposites with diverse mesostructures

On the basis of a sol–gel process, a facile, low cost, and one-step approach for preparing ordered magnetic mesoporous γ-Fe₂O₃/SiO₂ nanocomposites by an evaporation-induced self-assembly (EISA) approach is presented. Various mesostructured silica materials (P6mm or Im3m) incorporated with different amounts of iron oxide (n_Si/n_Fe=9/1, 8/2, 7/3, respectively) were synthesized and characterized by XRD, TEM, N₂-sorption analyses, and superconducting quantum interference device (SQUID) magnetometer. The HCl-leaching experiments together with TEM micrographs and nitrogen sorption analysis suggested that most of the γ-Fe₂O₃ domains of several nanometers were embedded in the silica walls, rather than dispersed in the mesopores, which could cause the significant pore clogging reported in some studies. The release behaviors of lysozyme from these magnetic porous nanocomposites were investigated for the possible application of drug targeting and control release. The influence of iron precursors was also studied and a possible mechanism was proposed. The hydrolysis of Fe³⁺ ions under weakly acidic conditions and the induced formation of SiOFe bonds may account for the synthesis of this kind of nanocomposite. These multifunctional nanostructured materials would have a wide range of applications in toxin removal, catalysis, waste remediation, and biological separation as well as novel drug-carrier technologies.     

让化学史走进计算化学课堂

阐述了化学史在计算化学课程教学中所起到的积极作用,介绍了利用计算化学史培养学生的科学思维、科学精神、科学态度等科学素养的具体措施以及计算化学史在培养学生的民族情感和科学情感等情感教育方面所起到的作用,并对教学实践的实施效果进行了评价调查。     

High-performance Liquid Chromatography Study of the Nitration Course of Tetrabutoxycalix[4]arene at the Upper Rim:Determination of the Optimum Conditions for the Preparation of 5,11,17-Trinitro-25,26,27,28-tetrabutoxycalix[4]arene

A selective nitration of calix[4]arene at the upper rim in one pot process was described by monitoring the time dependence of the distribution of products by high‐performance liquid chromatography (HPLC). The discrimination of five nitrated products was accomplished by molecular symmetry considerations and ¹H NMR analysis. As a result, unusual 5,11,17‐trinitrocalix[4]arene ( 2d ) was obtained in 57% isolated yield. 5,11‐Dinitro‐calix[4]arene ( 2b ) and 5,11,17‐trinitrocalix[4]arene ( 2d ) with tetranitrocalix[4]arene 2e were further characterized by crystal X‐ray diffraction analysis. Furthermore, as an example of potential application, trinitrocalix[4]arene 2d could be converted to triaminocalix[4]arene 3d conveniently.     

PCVD氮化硼膜形成过程及表面形貌的分析

采用红外分析、金相技术及和透射电子显微(TEM)技术分析了射频PCVD法沉积氮化硼膜的形成过程.结果表明,在沉积过程中,非晶态氮化硼(a-BN)作为领先相首先按平面方式生长,然后立方氮化硼(c-BN)在其上成核,并靠沉积原子表面迁移过程而长大,这种过程交替进行的结果,使膜层由a-BN和c-BN组成.膜层的表面呈层状+胞状形貌,说明薄膜的生长不仅取决于固体表面的扩散,而且也与气相成分的扩散有关.     

Exploring the Dual Characteristics of CH3OH Adsorption to Metal Atomic Structures on Si (111)-7 × 7 Surface

Metal atoms were deposited on an Si (111)-7 × 7 surface, and they were adsorbed with alcohol gases (CH₃OH/C₂H₅OH/C₃H₇OH). Initially, C_nH_2n+1OH adsorption was simply used as an intermediate layer to prevent the chemical reaction between metal and Si atoms. Through scanning tunneling microscopy (STM) and a mass spectrometer, the C_nH_2n+1OH dissociation process is further derived as the construction of a surface quasi-potential with horizontal and vertical directions. With the help of three typical metal depositions, the surface characteristics of CH₃OH adsorption are more clearly presented in this paper. Adjusting the preheating temperature, the difference of thermal stability between CH₃O^– and H⁺ could be obviously derived in Au deposition. After a large amount of H⁺ was separated, the isolation characteristic of CH₃O^– was discussed in the case of Fe deposition. In the process of building a new metal-CH₃O^–-H⁺ model, the dual characteristics of CH₃OH were synthetically verified in Sn deposition. CH₃O^– adsorption is prone to influencing the interaction between the metal deposition and substrate surface in the vertical direction, while H⁺ adsorption determines the horizontal behavior of metal atoms. These investigations lead one to believe that, to a certain extent, the formation of regular metal atomic structures on the Si (111)-7 × 7-CH₃OH surface is promoted, especially according to the dual characteristics and adsorption models we explored.     

Simultaneous Hydrogen Generation and Exciplex Stimulated Emission in Photobasic Carbon Dots

Photocatalytic water splitting is a promising approach to generating sustainable hydrogen. However, the transport of photoelectrons to the catalyst sites, usually within ps-to-ns timescales, is much faster than proton delivery (∼μs), which limits the activity. Therefore, the acceleration of abstraction of protons from water molecules towards the catalytic sites to keep up with the electron transfer rate can significantly promote hydrogen production. The photobasic effect that is the increase in proton affinity upon excitation offers means to achieve this objective. Herein, we design photobasic carbon dots and identify that internal pyridinic N sites are intrinsically photobasic. This is supported by steady-state and ultrafast spectroscopic measurements that demonstrate proton abstraction within a few picoseconds of excitation. Furthermore, we show that in water, they form a unique four-level lasing scheme with optical gain and stimulated emission. The latter competes with photocatalysis, revealing a rather unique mechanism for efficiency loss, such that the stimulated emission can act as a toggle for photocatalytic activity. This provides additional means of controlling the photocatalytic process and helps the rational design of photocatalytic materials.     

Genome-wide association studies combined with k-fold cross-validation identify rs17822931 as an ancestry-informative marker in Han Chinese population

DNA-based ancestry inference has long been a research hot spot in forensic science. The differentiation of Han Chinese population, such as the northern-to-southern substructure, would benefit forensic practice. In the present study, we enrolled participants from northern and southern China, each participant was genotyped at ∼400 K single-nucleotide polymorphisms (SNPs) and data of CHB and CHS from 1000 Genomes Project were used to perform genome-wide association analyses. Meanwhile, a new method combining genome-wide association study (GWAS) analyses with k-fold cross-validation in a small sample size was introduced. As a result, one SNP rs17822931 emerged with a p-value of 7.51E − 6. We also simulated a huge dataset to verify whether k-fold cross-validation could reduce the false-negative rate of GWAS. The identified ABCC11 rs17822931 has been reported to have allele frequencies varied with the geographical gradient distribution in humans. We also found a great difference in the allele frequency distributions of rs17822931 among five different cohorts of the Chinese population. In conclusion, our study demonstrated that even small-scale GWAS can also have potential to identify effective loci with implemented k-fold cross-validation method and shed light on the potential maker of rs17822931 in differentiating the north-to-south substructure of the Han Chinese population.     

Improvement on mixed-potential type ammonia sensor by a Cr2O3 gas-phase catalyst layer

Journal of Solid State Electrochemistry - Mixed-potential type ammonia sensors based on yttria-stabilized zirconia are promising devices in NOx reducing system for high-temperature exhaust....