Giant Asymmetric Transmission and Circular Dichroism with Angular Tunability in Chiral Terahertz Metamaterials

Inspired by the chiral structure from mode interaction, a chiral terahertz metamaterial and its complementary structure with the coexistence of asymmetric transmission and circular dichroism response are designed. The asymmetric transmission happens in the presence of electric and magnetic modes perpendicular to each other, resulting from intrinsic chirality under normal incidence. Circular dichroism exists in the presence of electric and magnetic modes parallel to each other under oblique incidence because of extrinsic chirality. Both asymmetric transmission and circular dichroism are enhanced by complementary structures, benefitting from the coupling between adjacent units. The maximum of chiral parameter κ can achieve 450, which is one hundred times higher than previously reported. The chiral response can be tuned by the incident angle and is sensitive to the environmental refractive index. The results highlight the potential applications of these metamaterials in chiral sensing and polarization transformation devices.     

负反馈诱发神经电振荡的反常现象的复杂动力学

传统观念认为,负反馈容易使系统达到稳定平衡点而正反馈容易引起振荡.本研究基于神经元理论模型,提出了负反馈可以诱发稳定平衡点、也就是静息、变为振荡、也就是放电的新观点.在Hopf分岔点附近,作用在静息上的一次足够大的负向脉冲电流的抑制性刺激,能够引起一个动作电位及随后的衰减振荡的后电位;而能够在后电位上诱发出动作电位的负脉冲电流强度阈值也是衰减振荡的.在模型中,引入具有时滞($\tau$)的负反馈来模拟抑制性自突触,一个动作电位诱发的负反馈自突触电流会作用到比动作电位延迟$\tau$的后电位上.随时滞增加,能够诱发出放电的负反馈增益强度阈值呈现出具有衰减振荡特点的类似多重相干共振的特性,衰减振荡的周期与电流阈值曲线的周期以及分岔点附近的放电周期相关.另外,负反馈还能诱发出放电与静息共存的复杂行为.本研究的结果不仅揭示了负反馈的新的反常调控作用,还有助于理解在现实神经系统中存在的慢抑制性自突触的潜在功能.      

时滞Rucklidge系统Hopf分岔分析与电路实现

以一类新的单时滞Rucklidge系统为分析对象,通过计算时滞系统的平衡点,分析该系统在各平衡点的稳定性和Hopf分岔的存在性,得到其发生Hopf分岔的条件。Matlab多组数值仿真验证了理论分析的正确性。基于此设计了一种可切换时滞与非时滞的混沌电路,并运用Multisim14.0进行仿真,实验结果表明,该电路可行且有效。     

Linear response theory of ion excitation for Fourier transform mass spectrometry

A linear relation between the voltage density or magnitude spectrum of an excitation waveform and the corresponding ion orbital radius is derived for Fourier transform mass spectrometry (FTMS). This provides a theoretical foundation for the stored waveform inverse Fourier transform excitation method. The result is also useful for the design of optimal excitation signals as well as for the estimation of the kinetic energy of ions after an excitation event in collision-induced dissociation experiments. When the linear relation is applied to two-dimensional FTMS excitation, an analytical expression for ion speed modulation is obtained.     

Bruch’s-Mimetic Nanofibrous Membranes Functionalized with the Integrin-Binding Peptides as a Promising Approach for Human Retinal Pigment Epithelium Cell Transplantation

Background: This study aimed to develop an ultrathin nanofibrous membrane able to, firstly, mimic the natural fibrous architecture of human Bruch’s membrane (BM) and, secondly, promote survival of retinal pigment epithelial (RPE) cells after surface functionalization of fibrous membranes. Methods: Integrin-binding peptides (IBPs) that specifically interact with appropriate adhesion receptors on RPEs were immobilized on Bruch’s-mimetic membranes to promote coverage of RPEs. Surface morphologies, Fourier-transform infrared spectroscopy spectra, contact angle analysis, Alamar Blue assay, live/dead assay, immunofluorescence staining, and scanning electron microscopy were used to evaluate the outcome. Results: Results showed that coated membranes maintained the original morphology of nanofibers. After coating with IBPs, the water contact angle of the membrane surfaces varied from 92.38 ± 0.67 degrees to 20.16 ± 0.81 degrees. RPE cells seeded on IBP-coated membranes showed the highest viability at all time points (Day 1, p < 0.05; Day 3, p < 0.01; Days 7 and 14, p < 0.001). The proliferation rate of RPE cells on uncoated poly(ε-caprolactone) (PCL) membranes was significantly lower than that of IBP-coated membranes (p < 0.001). SEM images showed a well-organized hexa/polygonal monolayer of RPE cells on IBP-coated membranes. RPE cells proliferated rapidly, contacted, and became confluent. RPE cells formed a tight adhesion with nanofibers under high-magnification SEM. Our findings confirmed that the IBP-coated PCL membrane improved the attachment, proliferation, and viability of RPE cells. In addition, in this study, we used serum-free culture for RPE cells and short IBPs without immunogenicity to prevent graft rejection and immunogenicity during transplantation. Conclusions: These results indicated that the biomimic BM-IBP-RPE nanofibrous graft might be a new, practicable approach to increase the success rate of RPE cell transplantation.     

Designed fabrication of mesoporous silica-templated self-assembled theranostic nanomedicines

Theranostic nanosystems that integrate diagnosis and therapy have garnered increasing attention for personalized medicine.The integration of the versatile nanoparticles to fabricate self-assembled theranostic nanomedicines becomes increasingly important in current medical research.Mesoporous silica nanoparticles(MSN)with their highly attractive physicochemical properties and favorable morphological attributes represent ideal templates for the controlled assembly and integration of functional nanomaterials to fabricate self-assembled theranostic nanomedicines.The rationally designed combination strategy and heterostructure will improve the overall bioavailability and preserve the unique property of each nanocomponent.In this review,the cutting-edge strategies for the designed fabrication of MSN-templated self-assembled nanomedicines are summarized.We categorize MSN-based nanomedicines by their unique heterostructures,including core-shell,yolk-shell,core-satellite,heterodimer and core-shell-satellite structures,and discuss the controlled assembly approaches as well as the intriguing applications for disease theranostics.Finally,a perspective on the challenges in the clinical translation of self-assembled theranostic nanomedicines is highlighted.     

大学无机化学实验中碱式碳酸铜制备方法探讨

探讨大学无机化学实验中有关碱式碳酸铜制备的实验方法,并以Cu(NO3)2为原料、NaOH和Na2CO3的混合液为沉淀剂制备碱式碳酸铜。讨论反应物最佳配比、pH、温度等因素对产品的影响,并对所制产品进行XRD分析,提出一种制备碱式碳酸铜的大学无机化学实验方法。     

万古霉素手性固定相分离曼尼希碱类化合物对映体

采用大环抗生素类万古霉素手性固定相高效液相色谱法研究了一系列曼尼希碱类化合物的手性分离情况,并讨论了流动相中有机相的种类和比例、缓冲盐的种类和浓度、pH和柱温对该类化合物手性分离的影响。最佳实验条件为:乙腈:硝酸铵(35mmol/L,pH3.8)=15∶85(V/V),柱温15℃,流速0.6mL/min,检测波长300nm;四氢呋喃:硝酸铵(20mmol/L,pH4)=15∶85(V/V),柱温15℃,流速0.6mL/min,检测波长350nm。通过对比研究8种曼尼希碱类化合物的色谱行为,从结构上讨论了化合物中各种官能团对手性分离的影响,并探讨了手性分离的内在机制。     

The chloro-substituent enhances performance of 2,4-bis (imino)pyridylchromium catalysts yielding highly linear polyethylene

The five unsymmetrical 2-[1-(2,4-dibenzhydryl-6-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine compounds (aryl: 2,6-Me₂Ph L1 , 2,6-Et₂Ph L2 , 2,6-ⁱPr₂Ph L3 , 2,4,6-Me₃Ph L4 and 2,6-Et₂–4-MePh L5 ) were prepared and characterized with FT-IR and ¹H/¹³C NMR spectroscopy as well as elemental analysis. The treatment of L1 – L5 with CrCl₃·3THF affords the corresponding chromium chloride complexes ( Cr1 – Cr5 ) in excellent yields. The molecular structures of Cr2 and Cr3 characterized by X-ray diffraction show a distorted octahedral geometry with three nitrogen atoms and three chlorine atoms around the metal center. On activation with either MAO or MMAO, Cr1 – Cr5 collectively display high activity (up to 14.96 × 10⁶ g (PE) mol⁻¹ (Cr) h⁻¹ at 60 °C) affording highly linear polyethylene with low molecular weight distribution (M_w/M_n) ranging from 1.06 to 2.81. An in-depth catalytic evaluation of Cr1 was conducted in order to investigate how the cocatalyst type and its amount, reaction temperature and polymerization time affect the catalytic activities and polymer properties.     

Metabolomics analysis of the therapeutic mechanism of Semen Descurainiae Oil on hyperlipidemia rats using 1H‐NMR and LC–MS

Semen descurainiae oil (SDO) is an important traditional Chinese medicine that was recently discovered to have the function of reducing blood lipids. Metabolomics analyses of plasma, liver and kidney in rats were performed using ¹H‐NMR and LC–MS to illuminate the lower blood lipid concentration effect of SDO, and niacin was considered as the active control. The measure of total cholesterol (TC) and low‐density‐lipoprotein cholesterol (LDL‐C) in plasma showed that SDO treatment decreased significantly the content of TC and LDL‐C. An orthogonal partial least squares–discriminant analysis approach was applied to identify the different metabolic profiles of plasma, liver and kidney in rats and to detect related potential biomarkers. The results suggested that the metabolic profiles of the control group and hyperlipidemia group showed significant difference and the SDO and niacin group had effective anti‐hyperlipidemia function. The biomarkers primarily concern lipid metabolism, amino acid metabolism and glycometabolism, and the change in biomarkers indicated that hyperlipidemia could cause the unbalance of these metabolic pathways in vivo. SDO reduced blood lipids by repairing amino acid and lipid metabolism.