The effect of surfactant concentration on the geometry of pores resulting from etching of poly(ethylene naphthalate) films irradiated by high-energy ions

The influence of temperature and concentrations of an alkali and a surfactant in etching solutions on the structural and transport characteristics of membranes produced by etching latent tracks of high-energy heavy ions in poly(ethylene naphthalate) films has been studied. The presence of a surfactant provides the formation of spindle-shaped pores narrowing in the direction toward the film surfaces. A procedure has been developed for the quantitative assessment of the degree of widening of spindle-shaped pores in their central part. The transport properties of track membranes with spindle-shaped and cylindrical pores have been compared.     

Diffraction filters based on polyimide and poly(ethylene naphthalate) track membranes

The problem of optical filters for soft x rays and extreme ultraviolet that provide a high degree of blocking ultraviolet and visible background radiations is considered. The subject of discussion is the filter based on a track membrane, a polymer film with micrometer and submicrometer pores, rather than the standard thin-film system. It is proposed that the membranes be made of poly(ethylene naphthalate) or polyimide, the UV absorption edge of which lies near the boundary of the visible range. The properties of poly(ethylene naphthalate) and polyimide membranes are contrasted with those of conventional porous poly(ethylene terephthalate) films, which are obtained by ion track etching. The spectral characteristics of poly(ethylene naphthalate) and polyimide films, as well as the formation of “track” pores when the specimens are successively treated by fast ions and chemicals, are studied. The basic parameters of the resulting porous structures are examined, and treatment conditions under which desired optical properties of the membranes are achieved are found. Filters based on poly(ethylene naphthalate) and polyimide track membranes may be applied in x-ray astronomy as constituents of detectors incorporated into solar telescopes and in experiments with the laboratory plasma.     

Anisotropic mesh refinement in stabilized Galerkin methods

Summary. The numerical solution of a convection-diffusion-reaction model problem is considered in two and three dimensions. A stabilized finite element method of Galerkin/Least-square type accomodates diffusion-dominated as well as convection- and/or reaction-dominated situations. The resolution of boundary layers occuring in the singularly perturbed case is achieved using anisotropic mesh refinement in boundary layer regions. In this paper, the standard analysis of the stabilized Galerkin method on isotropic meshes is extended to more general meshes with boundary layer refinement. Simplicial Lagrangian elements of arbitrary order are used. Received March 6, 1995 / Revised version received August 18, 1995     

A Priori Error Estimates for Finite Element Methods for H (2,1)-Elliptic Equations

The convergence of finite element methods for linear elliptic boundary value problems of second and forth order is well understood. In this article, we introduce finite element approximations of some linear semi-elliptic boundary value problem of mixed order on a two-dimensional rectangular domain Q. The equation is of second order in one direction and forth order in the other and appears in the optimal control of parabolic partial differential equations if one eliminates the control and the state (or the adjoint state) in the first order optimality conditions. We establish a regularity result and estimate for the finite element error of conforming approximations of this equation. The finite elements in use have a tensor product structure, in one dimension we use linear, quadratic or cubic Lagrange elements in the other dimension cubic Hermite elements. For these elements, we prove the error bound O(h ² + τ ^k ) in the energy norm and O((h ² + τ ^k )(h ² + τ)) in the L ²(Q)-norm.     

DC-60 heavy ion cyclotron complex: The first beams and project parameters

The construction of the DC-60 Heavy Ion Cyclotron for the Interdisciplinary Scientific Research Complex (ISRC) in Astana started in early 2004. The cyclotron was manufactured and tested at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna. The main units were delivered to Astana and assembled in the ISRC building in the summer of 2006. The cyclotron was turned on in September, 2006. The first heavy ion beams in the whole A/Z and energy ranges were accelerated and extracted in December, 2006. The complex, based on the DC-60 cyclotron, is intended for applied and fundamental research using accelerated heavy ion beams ranging from Carbon to Xenon with energies in the range of 0.34–1.77 MeV/nucleon, as well as for experiments on the channel of low energy ion beams, where the ion extraction voltage supplied by the ECR source reaches 25 kV. The energy variation of the accelerated ions is accomplished by changing the ion charge. The possibility of smoothly tuning the ion energy by ±30% of its nominal value can be seen by changing the cyclotron magnetic field. Within the framework of commissioning the DC-60 cyclotron, a number of experiments were carried out with accelerating charged particle beams in the main points of the working diagram

On a Conjecture of R.P. Stanley; Part II—Quotients Modulo Monomial Ideals

In 1982 Richard P. Stanley conjectured that any finitely generated ⁿ -graded module M over a finitely generated ⁿ -graded K-algebra R can be decomposed as a direct sum M = _{i = 1} ^t _i S _i of finitely many free modules _i S _i which have to satisfy some additional conditions. Besides homogeneity conditions the most important restriction is that the S _i have to be subalgebras of R of dimension at least depth M.We will study this conjecture for modules M = R/I, where R is a polynomial ring and I a monomial ideal. In particular, we will prove that Stanley's Conjecture holds for the quotient modulo any generic monomial ideal, the quotient modulo any monomial ideal in at most three variables, and for any cogeneric Cohen-Macaulay ring. Finally, we will give an outlook to Stanley decompositions of arbitrary graded polynomial modules. In particular, we obtain a more general result in the 3-variate case.     

Alkyl-Resorcinol Derivatives as Inhibitors of GDP-Mannose Pyrophosphorylase with Antileishmanial Activities

Leishmaniasis is a vector-borne disease caused by the protozoan parasite Leishmania found in tropical and sub-tropical areas, affecting 12 million people around the world. Only few treatments are available against this disease and all of them present issues of toxicity and/or resistance. In this context, the development of new antileishmanial drugs specifically directed against a therapeutic target appears to be a promising strategy. The GDP-Mannose Pyrophosphorylase (GDP-MP) has been previously shown to be an attractive therapeutic target in Leishmania. In this study, a chemical library of 5000 compounds was screened on both L. infantum (LiGDP-MP) and human (hGDP-MP) GDP-MPs. From this screening, oncostemonol D was found to be active on both GDP-MPs at the micromolar level. Ten alkyl-resorcinol derivatives, of which oncostemonols E and J (2 and 3) were described for the first time from nature, were then evaluated on both enzymes as well as on L. infantum axenic and intramacrophage amastigotes. From this evaluation, compounds 1 and 3 inhibited both GDP-MPs at the micromolar level, and compound 9 displayed a three-times lower IC₅₀ on LiGDP-MP, at 11 µM, than on hGDP-MP. As they displayed mild activities on the parasite, these compounds need to be further pharmacomodulated in order to improve their affinity and specificity to the target as well as their antileishmanial activity.     

Adsorption of anionic surfactant on porous and non-porous polyethylene terephthalate films

We study the adsorption of anionic surfactant, sodium dodecyl diphenyloxide disulfonate (SDDD) on three types of polyethylene terephthalate substrates from aqueous solutions of SDDD of different concentrations. Neutral electrolyte (KCl) was added to the solutions to vary the ionic strength. The three types of substrates were: (1) original polymer film, (2) etched non-porous film, which was obtained from pristine film by chemical etching and bears negative charge on the surface, (3) etched porous membranes, which were fabricated from pristine film by ion irradiation and subsequent chemical etching. The membranes have negative charge on the flat surface and on the inner pore walls. The comparison of original and etched nonporous films shows that the negative charge on the flat surface has weak effect on adsorption of the anionic surfactant. The comparison of etched non-porous and porous films shows that the SDDD adsorption on the inner walls of pores is much weaker than on flat surface—even in case the pore radius is significantly larger than the Debye length. This “exclusion” effect strongly depends on ionic strength of solution. For the porous films, the effect of the pore size and shape on the anionic surfactant adsorption is presented and discussed.