The problem of the convexity of the Bernstein-Bezier surface is one of the major comcernsin Computer Aided Geometric Design. The Convexity of the B-B surface is closely related to its controlnet, but how to define the B-net for the B-B surface over a rectangle has not been solved well. In thispaper, a concept of a natural net is presented and it is proved that a natural net with strong convexityis capable of in variance of the degree elevation.
No σ-conjugation effect can take place be-tween the three separated three-center bonds in B3H9,whose proper-ties are fB-B=4.5964 nJ/m,fB-Hb-B=32.3066 nJ/m,fHb3cen=42.1337 nJ/m.
The optimization calculations show that B(32) is the most stable cluster when 12 five-coordinated and 20 six-coordinated borons are not in the same spherical surface. Two kinds of obtained B─B distances (R(56),R(66)) verify Lipscomb's a set of empirical values.
Senbao I # can inhibit excessive growth and keep rejanenescence for larch seedling: A-B-B and A-B-C combination is optimum when those fungicides are mixed use.
The relationship between Lagrange curves and B B curves is studied. A method of formulating a curve of polynomials with d degree is presented in which the end information is d i d t iG(j)(j=0,1,i=1,2,…,r<) and the inner information is P i=G(t i)(0
Conserved hypothetical BB0462 protein enhances the transcription activity of oppAV promoter
Borrelia burgdorferi BB0462 ORF encodes an unknown functional protein with 110 amino acids.
The co-transformation of BB0462 ORF and oppA upstream regulation DNA into E.
coli host cells and β-galactosidase activity assay demonstrated that the BB0462 protein enhanced the transcriptional activity of the oppAV promoter, but does not affect those of oppAI, II, III and IV promoters.
Analysis of DNA retardation and competitive repression also confirmed that the BB0462 protein bound to the 409 bp upstream regulation DNA fragment close to the initiation codon of the oppAV gene.
A more general mathematical analysis of the kinetics of polycondensation-depolycondensation reactions is given in the article. Three different types of reactions are considered, namely, (1) reactions between molecules AB and AB, (2) reactions between molecules AA and BB, (3) reactions between molecules AA and BC. One of the condensation products is assumed (without loss of generality) to be water.For reactions of the first type, [p_n], the number of molecules of the n-mer (AB)_n, obeys the following Flory...
A more general mathematical analysis of the kinetics of polycondensation-depolycondensation reactions is given in the article. Three different types of reactions are considered, namely, (1) reactions between molecules AB and AB, (2) reactions between molecules AA and BB, (3) reactions between molecules AA and BC. One of the condensation products is assumed (without loss of generality) to be water.For reactions of the first type, [p_n], the number of molecules of the n-mer (AB)_n, obeys the following Flory distribution: [p_n]=N_0p~(n-1)(1-p)~2 where N_0 denotes the total number of AB segments (including the unreacted monomers). and p, as defined by is a measure of the degree of condensation. It is shown that p is the solution of the following differential equation: dp/dt=k/2N_0(1-p)~2-k_(-1)p[H_2O] where K and k_(-1) are velocity constants of condensation and hydrolysis respectively, and [H_2O] denotes the number of water molecules. Three special cases are discussed.For reactions of the second type, three different types of condensation products are possible besides water; they obey the following distributions: [p_(2n)]=2N′_0r~(n-1)p~(2n-1)(1-p)(1-rp) [p′_(2n-1)]=N′_0r~(n-1)p~(2n-2)(1-p)~2 [p″_(2n-1)]=N′_0r~(n-2)p~(2n-2)(1-rp)~2 where N′_0 and N″_0 denote the total number of segments AA and BB respectively, r denotes the ratio N′_0/N″_0, and p, as defined by is the solution of the following differential equation: dp/dt=kn′_0/r(1-p)(1-rp)-k_(-1)P[H_2O]For reactions of the third type, six different types of condensation products are possible besides water; they obey the following distributions: [P′_(2n)]=NP~(n-1)q~n(1-p/2-q/2)(1-p) [p″_(2n)]=Np~nq~(n-1)(1-p/2-q/2_(?))(1-q) [p_(2n-1)=Np~(n-1)q~(n-1)(1-p/2-q/2)~2 [p′_(2n-1)]=N/4p~(n-2)q~n(1-p)~2 [p″_(2n-1)]=N/4p~nq~(n-2)(1-p)~2 [p′″_(2n-n)]=∈(n)N/4p~(n-1)q~(n-1)(1-p)(1-q),where N denotes either the total number of segments AA or that of BC, while p and q, as defined by satisfy the following set of differential equations: dp/dt=k′N/2(1-p)(2-p-q)-k′_(-1)p[H_O] dq/dt=k″N/2(1-q)(2-p-q)-k″_(-1)q[H_2O]
1.The principal reactions of methylcyclohexane,methylcyclopentane and heptane on platinum-fluorine-alumina catalyst of various platinum and hydrogen fluoride contents(Pt,0～1%;HF,0～5%)have been investigated under fixed reaction conditions:temperature,472℃,pressure,20 atm.,LHSV,3,H_2:feed (mol.ratio),6:1.The main results of present investigation are found to be in good agreement with the reaction machanism and the dual function of“houdri- forming” catalyst suggested by Mills and Heinemann.Platinum-fluorine- alumina...
1.The principal reactions of methylcyclohexane,methylcyclopentane and heptane on platinum-fluorine-alumina catalyst of various platinum and hydrogen fluoride contents(Pt,0～1%;HF,0～5%)have been investigated under fixed reaction conditions:temperature,472℃,pressure,20 atm.,LHSV,3,H_2:feed (mol.ratio),6:1.The main results of present investigation are found to be in good agreement with the reaction machanism and the dual function of“houdri- forming” catalyst suggested by Mills and Heinemann.Platinum-fluorine- alumina catalyst consists of two important kinds of active sites,i.e.the dehy- drogenation(or metal)site and the isomerization(or acid)site;the former is derived from platinum and the latter from hydrogen fluoride.Dehydroisomeri- zation of methylcyclopentane and isomerization of n-heptane can proceed effec- tively only upon the dual site catalyst. 2.With platinum content fixed at 0.3%,the following results for the effect of hydrogen fluoride on the reactions of methylcyclopentane and n-heptane are obtained:for HF content below 1%,benzene yield of methylcyclopentane increases by increasing hydrogen fluoride content,for HF content greater than 1%,no further appreciable influence is observed.Isomerization of n-heptane is easier than dehydroisomerization of methylcyclopentane,so that catalyst of 0.2% HF is very efficient for isomerization of n-heptane.The major effect of hydrogen fluoride in excess of 0.2% is to accelerate hydrocracking reaction and thereby decrease liquid yield remarkably.A short discussion for these experimental re- sults is presented with the use of the recent information published by Wēbb, which shows how the surface acid strength of alumina is influenced by vary- ing the content of hydrogen fluoride.
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