烦人的二级光谱线

本利用光学知识说明了二级光谱线难以寻找的原因，从而要求在实验过程中．除了耐心、仔细外，在词节仪器的时候还要做到“一适中，二清晰，三合一”。     

Differential effects of thiopeptide and orthosomycin antibiotics on translational GTPases

The ribosome is a major target in the bacterial cell for antibiotics. Here, we dissect the effects that the thiopeptide antibiotics thiostrepton (ThS) and micrococcin (MiC) as well as the orthosomycin antibiotic evernimicin (Evn) have on translational GTPases. We demonstrate that, like ThS, MiC is a translocation inhibitor, and that the activation by MiC of the ribosome-dependent GTPase activity of EF-G is dependent on the presence of the ribosomal proteins L7/L12 as well as the G' subdomain of EF-G. In contrast, Evn does not inhibit translocation but is a potent inhibitor of back-translocation as well as IF2-dependent 70S-initiation complex formation. Collectively, these results shed insight not only into fundamental aspects of translation but also into the unappreciated specificities of these classes of translational inhibitors.     

On non-Newtonian lubrication with the upper convected Maxwell model

A long-standing theoretical and practical problem, whether the viscoelasticity can have a measurable and beneficial effect on lubrication performance characteristics, is readdressed in this paper. The upper convected Maxwell model is chosen to study the influence of viscoelasticity on lubricant thin film flows. By employing characteristic lubricant relaxation times in an order of magnitude analysis, a perturbation method is developed for analysing the flow of a Maxwell lubricant between two narrow surfaces. The effect of viscoelasticity on the lubricant velocity and pressure is examined, and the influence of minimum film thickness on lubrication characteristics is investigated. An order of magnitude analysis reveals that the pressure distribution is significantly affected by the presence of fluid viscoelasticity when the minimum film thickness is sufficiently small. This mechanism suggests that viscoelasticity does indeed enhance the lubricant pressure field and produce a beneficial effect on lubrication performance, which is consistent with some experimental observations.     

星型两亲性聚己内酯-b-聚甲基丙烯酸(2-羟乙酯)嵌段共聚物的合成和表征

通过开环聚合(ROP)和原子转移自由基聚合(ATRP)制备了一类新型的两亲性嵌段共聚物——六臂星形聚(ε-已内酯)-b-聚甲基丙烯酸(2-羟乙酯)(6sPCL-b-PHEMA).6sPCL-b-PHEMA通过三步反应合成:(1)双季戊四醇开环聚合ε-己内酯的合成6sPCL;(2)以2-溴异丁基酰溴封端星形聚合物制备大分...     

The Traveling Wave of Auto-Catalytic Systems-Monotone and Multi-Peak Solutions

This article studies propagating wave fronts of a reaction-diffusion system modeling an isothermal chemical reaction $A+2B → 3B$ involving two chemical species, a reactant $A$ and an auto-catalyst $B$, whose diffusion coefficients, $D_A$ and $D_B$, are unequal due to different molecular weights and/or sizes. Explicit bounds $c_∗$ and $c^∗$ that depend on $D_B/D_A$ are derived such that there is a unique travelling wave of every speed $c ≥ c^∗$ and there does not exist any travelling wave of speed $c < c_∗$. Furthermore, the reaction-diffusion system of the Gray-Scott model of $A+2B → 3B$, and a linear decay $B → C$, where $C$ is an inert product is also studied. The existence of multiple traveling waves which have distinctive number of local maxima or peaks is shown. It shows a new and very distinctive feature of Gray-Scott type of models in generating rich and structurally different traveling pulses.     

Existence of Traveling Waves of General Gray-Scott Models

This work gives a rigorous proof of the existence of propagating traveling waves of a nonlinear reaction–diffusion system which is a general Gray-Scott model of the pre-mixed isothermal autocatalytic chemical reaction of order m (\(m > 1\)) between two chemical species, a reactant A and an auto-catalyst B, \( A + m B \rightarrow (m+1) B\), and a super-linear decay of order \( n > 1\), \( B \rightarrow C\), where \( 1< n < m\). Here C is an inert product. Moreover, we establish that the speed set for existence must lie in a bounded interval for a given initial value \(u_0\) at \( - \infty \). The explicit bound is also derived in terms of \(u_0\) and other parameters. The same system also appears in a mathematical model of SIR type in infectious diseases.     

Singular solutions of parabolic -Laplacian with absorption

We consider, for and , the -Laplacian evolution equation with absorption

We are interested in those solutions, which we call singular solutions, that are non-negative, non-trivial, continuous in , and satisfy for all . We prove the following:

(i)

When , there does not exist any such singular solution.

(ii)

When , there exists, for every , a unique singular solution that satisfies as .

Also, as , where is a singular solution that satisfies as .

Furthermore, any singular solution is either or for some finite positive .

     

Palladium-catalyzed sequential one-pot reaction of aryl bromides with O-homoallylhydroxylamines: synthesis of N-aryl-beta-amino alcohols

The palladium-catalyzed sequential one-pot N-arylation-carbo-amination-C-arylation of O-homoallylhydroxylamines with two different aryl bromides provides rapid entry to differentially arylated N-aryl-3-arylmethylisoxazolidines in good yields with excellent diastereoselectivity. The obtained isoxazolidines can be reductively cleaved to cis-N-aryl-beta-amino alcohols in short times and in high yields at room temperature.     

Effect of carbon black type and concentration on the performance of semiconductive shielding material of high-voltage cable

Semiconductive shielding layer as an important part of high-voltage cable, its performance directly affects the safe operation and the service life of the cable. Carbon black (CB) is the main conductive filler of shielding materials, and its type and concentration directly affect the performance of the shielding layer. In this paper, CB-A with higher structure and CB-B with lower structure were used as conductive fillers and EBA was chosen as the matrix resin to prepare the shielding materials. The CB concentrations of the shielding materials were 35, 45, and 55 phr. The influences of CB type and concentration on the physicochemical, electrical, thermal and mechanical properties of the shielding materials were investigated. The research shows that when the CB types are the same, the higher the concentration of CB, the more intensive the CB network in the shielding material, and the more serious the CB agglomeration phenomenon. With increasing CB concentration, shielding materials show a decreasing trend of volume resistivity, an increasing trend of thermal conductivity, and a decreasing trend of mechanical properties. When the CB concentration is the equal, the CB-A has better dispersion in the matrix resin, CB-A/EBA shielding material has lower volume resistivity and weaker PTC effect, CB-A/EBA shielding material has higher thermal conductivity at low temperature and CB-B/EBA shielding material has higher thermal conductivity at high temperature, CB-A/EBA shielding material has better mechanical properties. A comprehensive comparison shows that CB-A/EBA shielding material with a concentration of 45 phr has excellent overall performance, with volume resistivity of 15.3 and 68 Ω·cm at 25°C and 90°C, respectively. The thermal conductivity is 0.434 W/(m K) at room temperature and 0.536 W/(m K) at 90°C. The stress is 31.08 MPa and the strain is 570.2%. This work has important reference for the selection of conductive fillers and performance improvement of semiconductive shielding materials.     

乙酰乙酸乙酯烯醇式与酮式GC/MS和GC/IR分析

采用ＧＣ／ＭＳ对乙酸乙酯烯醇式在不同离子源温度,接口温度,进样器温度,柱温等条件下的气相色谱行为进行了研究,用重氢交换法和高分辨质谱法对烯醇式和酮式的质谱进行了解析,并通过ＧＣ／ＩＲ研究了烯醇式和酮式的红外光谱。