抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素

钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致.     

Iterative, aqueous synthesis of beta3-oligopeptides without coupling reagents

The chemoselective synthesis of amides by decarboxylative couplings of alpha-ketoacids and isoxazolidines makes possible an iterative approach to poly-beta3-peptides. Peptide assembly occurs under aqueous conditions and requires no coupling reagents. The requisite isoxazolidine monomers are prepared in enantiopure form by a convenient two-step protocol starting from the appropriate aldehydes.     

How good are the proximal point algorithms?

Proximal point algorithms are applicable to a variety of settings in optimization. See Rockafellar, R.T. (1976), and Spingarn, J.E. (1981) for examples. We consider a simple idealized proximal point algorithm using gradient minimization on C² convex functions. This is compared to the direct use of the same gradient method with an appropriate mollifier. The comparison is made by determining estimates of the costrequired to reduce the function to a given precision E. Our object is to assess the potential efficiency of these algorithms even if we do not know how to realize this potential.

We find that for distant starting values, proximal point algorithms are considerably less laborious than a direct method. However there is no essential improvement in the complexity - only in the numerical factors. This negative conclusion holds for the entire family of proximal point algorithms based on the gradient methods of this paper.

The algorithms considered may be important for large scale optimization problems. In applications, the precision e that is desired is usually fixed. Assume this is the case and assume that one is given a family of problems parameterized by the dimension

n. Suppose further that for all n, the condition number Q (defined below) is bounded. Then it will be seen below that for all n sufficiently large our algorithms will require a smaller number of steps than a polynomial algorithm with cost n |Ine|     

On problems with bounded state variables

A set of first-order necessary conditions is obtained for the general control problem of Bolza with bounded state constraints of the form (t, x)0, =1,...,m. With the solution required to satisfy the vector differential equationsx=f(t, x, u), whereu is control, an important feature of this paper is in relaxing the assumption on the rank of the matrix _x f _u generally made in attacking problems of this type. This is accomplished even though the solution may have an infinite number of intervals satisfying (t, x)=0 for various .The preparation of this paper was sponsored in part by the US Army Research Office, Grant No. DA-31-214-ARO(D)-355.     

Second-order necessary conditions for general problems with state inequality constraints

Journal of Optimization Theory and Applications - This paper is a sequel to a previous article by the author, concerned with a certain canonical problem in optimal control involving constraints of...     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.