Zinc‐catalyzed transformation of diarylphosphoryl azides to diarylphosphate esters and amides

We have developed a facile and efficient procedure for the synthesis of diarylphosphate esters and amides. Using Zn(acac)₂ as the catalyst, the reaction of diarylphosphoryl azides with aliphatic alcohols and phenols through an unusual P?N bond cleavage provided a number of diarylphosphate esters in good yields (22 examples, up to 94%). Additionally, various diarylphosphate amides were obtained from the corresponding amines in excellent yields as well (8 examples, up to 96%).     

Correction: Cu-catalyzed C–C bond formation of vinylidene cyclopropanes with carbon nucleophiles

Correction for ‘Cu-catalyzed C–C bond formation of vinylidene cyclopropanes with carbon nucleophiles’ by Jichao Chen et al., Chem. Sci., 2019, 10, 10601–10606.

We regret that in the original article the structure of compound 1 in Tables 1–3 was incorrect. The correct structure is given below.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Numerical and Experimental Investigation of Liquid Residue in 90° Bend Microchannel Based on Gas–Liquid Two-Phase Flow

The microfluidic chip for nucleic acid detection in vitro is an essential application of microfluidic technology to the process of in vitro diagnosis. The 90° bend microchannels in chip designed for facilitating assay reagent delivery may cause reagent residues and cast mutual contamination between detection reagents, which significantly affects the detection accuracy. In this paper, a two-dimensional gas–liquid two-phase flow model is constructed to simulate the liquid residue phenomenon. Using the results of simulation, the residual liquid generation can be observed and the area of residual liquid can be obtained. The accuracy of the numerical simulation is verified by comparison with the experimental results. The effects of the fillet radius R, the diameter ratio d₁/d₂ of the vertical to horizontal sections, the flow velocity v, and the surface roughness R_a on the residual amount are studied. We find that the fillet radius is inversely proportional to the residual amount within the range v = 20–100 mm/s and there is almost no liquid residue in the channel when the radius increases to R = 1 mm. When the channel diameter ratio d₁/d₂ increases, the liquid residual amount also increases by approximately 98%. The increased surface roughness R_a significantly increases the residual amount. The results of this study provide a reference for the optimal design of microchannels on chips.

     

Rate-dependent asymmetric hysteresis modeling and robust adaptive trajectory tracking for piezoelectric micropositioning stages

Nonlinear Dynamics - Hysteresis is an inherent characteristic of piezoelectric materials that can be determined by not only the historical input but also the input signal frequency. Hysteresis...     

Dynamic and wear characteristics of self-lubricating bearing cage: effects of cage pocket shape

34,354,966 active cases and 460,787 deaths because of COVID-19 pandemic were recorded on November 06, 2021, in India. To end this ongoing global COVID-19 pandemic, there is an urgent need to implement multiple population-wide policies like social distancing, testing more people and contact tracing. To predict the course of the pandemic and come up with a strategy to control it effectively, a compartmental model has been established. The following six stages of infection are taken into consideration: susceptible (S), asymptomatic infected (A), clinically ill or symptomatic infected (I), quarantine (Q), isolation (J) and recovered (R), collectively termed as SAIQJR. The qualitative behavior of the model and the stability of biologically realistic equilibrium points are investigated in terms of the basic reproduction number. We performed sensitivity analysis with respect to the basic reproduction number and obtained that the disease transmission rate has an impact in mitigating the spread of diseases. Moreover, considering the non-pharmaceutical and pharmaceutical intervention strategies as control functions, an optimal control problem is implemented to mitigate the disease fatality. To reduce the infected individuals and to minimize the cost of the controls, an objective functional has been constructed and solved with the aid of Pontryagin’s maximum principle. The implementation of optimal control strategy at the start of a pandemic tends to decrease the intensity of epidemic peaks, spreading the maximal impact of an epidemic over an extended time period. Extensive numerical simulations show that the implementation of intervention strategy has an impact in controlling the transmission dynamics of COVID-19 epidemic. Further, our numerical solutions exhibit that the combination of three controls are more influential when compared with the combination of two controls as well as single control. Therefore, the implementation of all the three control strategies may help to mitigate novel coronavirus disease transmission at this present epidemic scenario.

     

Numerical appoximation of a channel flow problem

Our object in this article is to describe some numerical schemes for the approximation of a Channel Flow problem, and to study the stability of the schemes. Discretization is performed by the combination of spectral methods and finite difference methods.     

Practical Synthesis of New β‐Diketone‐Connected Bipyridine and Its Conversion to Pyrazole‐Centered Bipyridine Ligand

Two new polydentate ligands, 1‐(6‐hydroxymethyl‐2‐pyridyl)‐3‐(2‐pyridyl)‐propane‐1,3‐dione (6) and 1,3‐bis(6‐hydroxymethyl‐2‐pyridyl)‐propane‐1, 3‐dione (8), have been synthesized starting from 2,6‐pyridinedicarboxylic acid by conventional esterification, reduction, and condensation reactions. They were further converted to two new polydentate ligands, 3‐(6‐hydroxymethyl‐2‐pyridyl)‐5‐(2‐pyridyl)‐1H‐pyrazole (7) and 3,5‐bis(6‐hydroxymethyl‐2‐pyridyl)‐1H‐pyrazole (9), by reaction with hydrazine hydrate. These four compounds were characterized by proton nuclear magnetic resonance (¹H NMR), electrospray ionization‐mass spectrum (ESI‐MS), infrared spectrum (IR), and elemental analyses. The structure of 9 was also determined by X‐ray diffraction.     

磺化壳聚糖的制备及其对生长因子活性的保护作用

以壳聚糖为基材,分别以氯磺酸、三甲胺.三氧化硫和丙磺酸内酯为磺化试剂,制备了3,6-O-磺化壳聚糖(OCS)、2-N-磺化壳聚糖(NCS)和2-N-磺丙基壳聚糖(PCS)3种磺化壳聚糖.采用红外光谱、核磁共振谱证明了磺化壳聚糖的结构,元素分析测定了磺化壳聚糖的磺化率.以组织修复过程中一种重要的活性因子——碱性成纤维细胞生长因子(bFGF)为目标因子,通过体外成纤维细胞培养实验,评价了不同磺化壳聚糖对bFGF活性的保护能力.结果显示,相对于未改性壳聚糖(CS),磺化壳聚糖对成纤维细胞的形态无显著影响.细胞活性检测结果显示,OCS和PCS对bFGF活性无明显的保护能力;NCS能有效提高bFGF促进成纤维细胞活性的能力,其对bFGF活性的保护能力可达肝素70%左右.磺化壳聚糖的bFGF活性保护能力不随磺化率的改变而变化.