Manipulation of nonlinear optical responses in layered ferroelectric niobium oxide dihalides.

Realization of highly tunable second-order nonlinear optical responses, e.g., second-harmonic generation and bulk photovoltaic effect, is critical for developing modern optical and optoelectronic devices. Recently, the van der Waals niobium oxide dihalides are discovered to exhibit unusually large second-harmonic generation. However, the physical origin and possible tunability of nonlinear optical responses in these materials remain to be unclear. In this article, we reveal that the large second-harmonic generation in NbOX2 (X = Cl, Br, and I) may be partially contributed by the large band nesting effect in different Brillouin zone. Interestingly, the NbOCl2 can exhibit dramatically different strain-dependent bulk photovoltaic effect under different polarized light, originating from the light-polarization-dependent orbital transitions. Importantly, we achieve a reversible ferroelectric-to-antiferroelectric phase transition in NbOCl2 and a reversible ferroelectric-to-paraelectric phase transition in NbOI2 under a certain region of external pressure, accompanied by the greatly tunable nonlinear optical responses but with different microscopic mechanisms. Our study establishes the interesting external-field tunability of NbOX2 for nonlinear optical device applications.

Impacts of Proanthocyanidin Binding on Conformational and Functional Properties of Decolorized Highland Barley Protein.

The impacts of interaction between proanthocyanidin (PC) and decolorized highland barley protein (DHBP) at pH 7 and 9 on the functional and conformational changes in DHBP were investigated. It was shown that PC strongly quenched the intrinsic fluorescence of DHBP primarily through static quenching. PC and DHBP were mainly bound by hydrophobic interactions. Additionally, free sulfhydryl groups and surface hydrophobicity obviously decreased in DHBP after combining with PC. The zeta potential of DHBP-PC complexes at pH 7 increased significantly. A change in the structure of DHBP was caused by interactions with PC, resulting in an increase in the number of ß-sheets, a decrease in the number of α-helixes, and a spectral shift in the amide Ⅱ band. Furthermore, the presence of PC enhanced the foaming properties and antioxidant activity of DHBP. Overall, this study suggests that DHBP-PC complexes at pH 7 could be designed as a stable additive, and illustrates the potential applications of DHBP-PC complexes in the food industry.

Ultrathin quantum light source with van der Waals NbOCl2 crystal.

Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl2), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS2. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies1-4.

Effects of decolorization on aggregation behavior of highland barley proteins: Comparison with wheat proteins.

To explore effects of decoloration on highland barley proteins (HBPs) aggregation, physicochemicalproperties, structuralcharacteristics, and functional characteristics of decolorized highland barley proteins (DHBPs) were investigated. In order to compare the aggregation of HBPs, wheat proteins (WPs) were selected as a control group. The solubility, turbidity, particle size and surfacehydrophobicity of HBPs increased obviously (P < 0.05) after decoloration, but still lower than WPs. Electrophoretic analysis showed that the bands amount of HBPs and DHBPs were lower than WPs, while decolorization had no effect on the bands amount of HBPs. Moreover, chemical bonds contents of DHBPs were higher than HBPs, but significant lower (P < 0.05) than WPs. The Fourier-transform infrared spectroscope showed that secondary structures of HBPs were more flexible after decoloration. Besides, foaming property, emulsifying property and water holding capacity of DHBPs increased significantly (P < 0.05). To conclude, the aggregation behavior and functional properties of HBPs were improved by the decolorization.

Inference of a "Hot Ice" Layer in Nitrogen-Rich Planets: Demixing the Phase Diagram and Phase Composition for Variable Concentration Helium-Nitrogen Mixtures Based on Isothermal Compression.

Van der Waals (vdW) chemistry in simple molecular systems may be important for understanding the structure and properties of the interiors of the outer planets and their satellites, where pressures are high and such components may be abundant. In the current study, Raman spectra and visual observation are employed to investigate the phase separation and composition determination for helium-nitrogen mixtures with helium concentrations from 20 to 95% along the 295 K isothermal compression. Fluid-fluid-solid triple-phase equilibrium and several equilibria of two phases including fluid-fluid and fluid-solid have been observed in different helium-nitrogen mixtures upon loading or unloading pressure. The homogeneous fluid in helium-nitrogen mixtures separates into a helium-rich fluid (F1) and a nitrogen-rich fluid (F2) with increasing pressure. The triple-phase point occurs at 295 K and 8.8 GPa for a solid-phase (N2)11He vdW compound, fluid F1 with around 50% helium, and fluid F2 with 95% helium. Helium concentrations of F1 coexisted with the (N2)11He vdW compound or δ-N2 in helium-nitrogen mixtures with different helium concentrations between 40 and 50% and between 20 and 40%, respectively. In addition, the helium concentration of F2 is the same in helium-nitrogen mixtures with different helium concentrations and decreases upon loading pressure. Pressure-induced nitrogen molecule ordering at 32.6 GPa and a structural phase transition at 110 GPa are observed in (N2)11He. In addition, at 187 GPa, a pressure-induced transition to an amorphous state is identified.

Structure Determination, Mechanical Properties, Thermal Stability of Co2MoB4 and Fe2MoB4.

The precise determination of atomic position of materials is critical for understanding the relationship between structure and properties, especially for compounds with light elements of boron and single or multiple transition metals. In this work, the single crystal X-ray diffraction is employed to analyze the atomic positions of Co2MoB4 and Fe2MoB4 with a Ta3B4-type structure, and it is found that the lengths of B-B bonds connecting the two zig-zag boron chains are 1.86 Å and 1.87 Å, but previously unreported 1.4 Å. Co and Fe atoms occupy the same crystallographic position in lattice for the doped samples and the valence is close to the metal itself, and Co/Fe K-edge X-ray Absorption Fine Structure(XAFS) spectra of borides with different ratios of Co to Fe are collected to detect the local environment and chemical valence of Co and Fe. Vickers hardness and nano indentation measurements are performed, together with the Density Functional Theory (DFT) calculations. Finally, Co2MoB4 possess better thermal stability than Fe2MoB4 evaluated by Thermogravimetric Differential Thermal Analysis (TG-DTA) results.

Distributed Fusion Estimation for Stochastic Uncertain Systems With Network-Induced Complexity and Multiple Noise.

This article investigates an issue of distributed fusion estimation under network-induced complexity and stochastic parameter uncertainties. First, a novel signal selection method based on event trigger is developed to handle network-induced packet dropouts, as well as packet disorders resulting from random transmission delays, where the H2/H∞ performance of the system is analyzed in different noise environments. In addition, a linear delay compensation strategy is further employed for solving the complex network-induced problem, which may deteriorate system performance. Moreover, a weighted fusion scheme is used to integrate multiple resources through an error cross-covariance matrix. Several case studies validate the proposed algorithm and demonstrate satisfactory system performance in target tracking.

Studying APOE ɛ4 Allele Dose Effects with a Univariate Morphometry Biomarker.

BACKGROUND: A univariate neurodegeneration biomarker (UNB) based on MRI with strong statistical discrimination power would be highly desirable for studying hippocampal surface morphological changes associated with APOE ɛ4 genetic risk for AD in the cognitively unimpaired (CU) population. However, existing UNB work either fails to model large group variances or does not capture AD induced changes. OBJECTIVE: We proposed a subspace decomposition method capable of exploiting a UNB to represent the hippocampal morphological changes related to the APOE ɛ4 dose effects among the longitudinal APOE ɛ4 homozygotes (HM, N = 30), heterozygotes (HT, N = 49) and non-carriers (NC, N = 61). METHODS: Rank minimization mechanism combined with sparse constraint considering the local continuity of the hippocampal atrophy regions is used to extract group common structures. Based on the group common structures of amyloid-ß (Aß) positive AD patients and Aß negative CU subjects, we identified the regions-of-interest (ROI), which reflect significant morphometry changes caused by the AD development. Then univariate morphometry index (UMI) is constructed from these ROIs. RESULTS: The proposed UMI demonstrates a more substantial statistical discrimination power to distinguish the longitudinal groups with different APOE ɛ4 genotypes than the hippocampal volume measurements. And different APOE ɛ4 allele load affects the shrinkage rate of the hippocampus, i.e., HM genotype will cause the largest atrophy rate, followed by HT, and the smallest is NC. CONCLUSION: The UMIs may capture the APOE ɛ4 risk allele-induced brain morphometry abnormalities and reveal the dose effects of APOE ɛ4 on the hippocampal morphology in cognitively normal individuals.

Transient Study of Femtosecond Laser-Induced Ge2Sb2Te5 Phase Change Film Morphology.

Femtosecond laser-induced crystallization and ablation of Ge2Sb2Te5 (GST) phase change film is investigated by reflectivity pump-probing technology. Below the ablation threshold, the face-centered cubic structure (FCC) state in the central area can be formed, and cylindrical rims are formed in the peripheral dewetting zone due to the solidification of transported matter. The time of surface temperature dropping to the crystallization point needs about 30 ps for 5.86 mJ/cm2 and 82 ps for 7.04 mJ/cm2, respectively. At higher laser fluence, crystallization GST island structures appear in the central ablation region due to the extremely short heating time (100 ps). Furthermore, crystallization rate is faster than the ablation rate of the GST film, which is caused by different reflectivity.

Rb21.89W32.66O108: An Excellent Mid- and Far-IR Nonlinear-Optical Material with a Wide Band Gap.

IR nonlinear-optical (NLO) crystal is the important device in IR laser technology. Nevertheless, the application of most IR NLO crystals in high-power lasers is always limited by the low laser damage threshold (LDT), which is mainly caused by the narrow optical band gap (Eg). Here, the physical properties of the Rb21.89W32.66O108 (RWO) crystal with a longer absorption cutoff edge and a wide Eg were systematically studied for the first time. A preliminary measurement of the LDT was performed, and the result shows that RWO has a high powder LDT of about 42 times that of AgGaS2. In order to better understand the relationship between the structure and properties, the dipole moments of WO6 octahedra were accurately calculated and analyzed. Meanwhile, it was indicated that RWO exhibits an ideal frequency doubling strength with the type I phase matching. Finally, it was revealed that RWO has great application value as an IR NLO crystal.

Occurrence of multi-class mycotoxins in Menthae haplocalycis analyzed by ultra-fast liquid chromatography coupled with tandem mass spectrometry.

To determine the presence of multi-class mycotoxins in Menthae haplocalycis, a sample processing procedure based on a modified quick, easy, effective, rugged, and safe method, and a rapid and accurate testing method using ultra-fast performance liquid chromatography coupled with tandem mass spectrometry, was developed and validated. We systematically evaluated the methodology for multi-mycotoxin analysis in the Menthae haplocalycis samples, and chose matrix-matched calibration curves as a reference to calculate the recoveries. Overall, the average recoveries varied between 67.1 and 103%, with relative standard deviations ranging from 0.34 to 10.3%. The optimized and validated method was applied to detect the presence of the target mycotoxins in 40 batches of Menthae haplocalycis samples. Results showed that the levels of mycotoxins varied among the samples. The most prevalent mycotoxin was tentoxin, followed by alternariol, alternariol monomethyl ether, zearalenone, fumonisin B2 , fumonisin B1 , ochratoxin A, aflatoxin B1 , aflatoxin B2 , aflatoxin G1 , and T-2 toxin. The analytical method developed herein could be applied for the routine monitoring of multi-mycotoxins in Menthae haplocalycis.

[Study on influence of different storage environments and packaging materials on quality of Citri Reticulatae Pericarpium].

Traditional Chinese herbs are readily contaminated by mold that produced mycotoxins which are closly related to the herbs' external factors and external environments during the storage process. In this study, Citri Reticulatae Pericarpium was used as example, and the characteristics of traits, water content, active components (naringin, hesperidin, sinensetin, naringin, tangeretin) and the accumulation of aflatoxins (AFs) were selected as the evaluation indexes. Citri Reticulatae Pericarpium was stored under different environments and packaging materials for 12 months, and then the quality changes and mildew of Citri Reticulatae Pericarpium were examined. The results showed that the color of Citri Reticulatae Pericarpium was deepened after storage, but without mildew phenomenon. Besides, the sample storage in kraft paper and woven bags had varying degrees of moth phenomenon after 12 months storage, and the water content exceeded the limit of Chinese Pharmacopoeia. In addition, the contents of the five active constituents obviously decreased, especially for hesperidin, which did not meet the pharmacopoeia standard after storage. AFs were not detected in any of the tested samples. According to the results, we conclude that low temperature and humidity environment is more suitable for the storage of Citri Reticulatae Pericarpium, and that packaging materials should be further investigated. This study is of great significance for preventing the mold to contaminate the traditional Chinese medicine and ensuring the quality, effectiveness and safety of TCMs.

Determination and pharmacokinetic properties of arsenic speciation in Xiao-Er-Zhi-Bao-Wan by high-performance liquid chromatography with inductively coupled plasma mass spectrometry.

A method of high performance liquid chromatography with a Hamilton PRP-X100 ion-exchange column (250 × 4.1 mm id, 10 µm) coupled to inductively coupled plasma mass spectrometry was employed to generate a full concentration-time profile of arsenic speciation after oral administration. The results exhibited good linearity and revealed that, in the pills, the average arsenic concentration was 10105.4 ± 380.7 mg/kg, and in the water extraction solution, the inorganic As(III) and As(V) concentrations were 220.1 ± 12.6 and 45.5 ± 2.3 mg/kg, respectively. No trace of monomethyl arsenic acid was detected in any of the plasma samples. We then successfully applied the established methodology to examine the pharmacokinetics of arsenic speciation. The resulting data revealed that, after oral administration in rats, the plasma concentration of each arsenic species reached Cmax shortly after initial dosing, and that the distribution and elimination of As(V) was faster than that of As(III) and dimethyl arsenic acid. Additionally, the t1/2 values of As(V), As(III), and dimethyl arsenic acid were 3.4 ± 1.6, 14.3 ± 4.0, and 19.9 ± 1.6 h, respectively. This study provides references for the determination of arsenic speciation in mineral-containing medicines and could serve as a useful tool in measuring the true toxicity in traditional medicines that contain them.

[Quality control in Menthae Haplocalycis Herba and its decoction slices].

Menthae Haplocalycis Herba has been widely applied in such fields as food, cosmetics, daily necessities, medicine and health, due to its unique efficacy. However, as the safety of traditional Chinese medicines has been of increasing concern, the quality issue of Menthae Haplocalycis Herba and its decoction slices has become a key obstructive factor for exports. This article focused on the control over Menthae Haplocalycis Herba's adulterants, exogenous hazardous residues and internal properties (chemical compositions, spectrum effect relationship). Moreover, current studies on the quality of Menthae Haplocalycis Herba and its decoction slices, as well as the existing problems in recent years were systematically summarized in the expectation of improving the means of quality control of Menthae Haplocalycis Herba and its decoction slices, enhancing its quality standards, and ensuring the use safety and effectiveness.