A posteriori L2 error estimation on anisotropic tetrahedral finite element meshes

A new a posteriori L₂ norm error estimator is proposed for thePoisson equation. The error estimator can be applied to anisotropictetrahedral or triangular finite element meshes. The estimatoris rigorously analysed for Dirichlet and Neumann boundary conditions. The lower error bound relies on specifically designed anisotropicbubble functions and the corresponding inverse inequalities.The upper error bound utilizes non-standard anisotropic interpolationestimates. Its proof requires H² regularity of the Poisson problem,and its quality depends on how good the anisotropic mesh resolvesthe anisotropy of the problem. This is measured by a so-called‘matching function’. A numerical example supports the anisotropic error analysis.     

Symmetrische,gemischt substituierte Trisilylamine (RR′R″Si)3N

Zusammenfassung Gemischt substituierte Disilylamine (RRRSi)₂NH lassen sich von NaNH₂ zu reaktionsfähigen Natrium-bis-(silyl)-amiden metallieren, aus denen nach Umsetzung mit Organohalogensilanen und anschließender Alkoholyse der verbleibenden Si-Cl-Gruppen gemischt substituierte Trisilylamine (RRRSi)₃N mit R=(me), R, R=O(me); R,R=(me), R=O(et); R=(vi), R, R=O(me); R=(me), R=(vi), R=O(ⁱpr) dargestellt werden konnten.33. Mitt.:U. Wannagat, J. Pump undH. Bürger, Mh. Chem.94, 1013 (1963).Auszüge aus den DissertationenH. Bürger, TH Aachen 1962,P. Geymayer, TH Graz 1963, und der DiplomarbeitG. Torper, TH Graz 1962; vgl. auchU. Wannagat undH. Bürger, Angew. Chem.75, 95 (1963).     

Fast Photoresponse and Long Lifetime UV Photodetectors and Field Emitters Based on ZnO/Ultrananocrystalline Diamond Films

We have designed photodetectors and UV field emitters based on a combination of ZnO nanowires/nanorods (ZNRs) and bilayer diamond films in a metal–semiconductor–metal (MSM) structure. The ZNRs were fabricated on different diamond films and systematic investigations showed an ultra‐high photoconductive response from ZNRs prepared on ultrananocrystalline diamond (UNCD) operating at a lower voltage of 2 V. We found that the ZNRs/UNCD photodetector (PD) has improved field emission properties and a reduced turn‐on field of 2.9 V μm^?1 with the highest electron field emission (EFE) by simply illuminating the sample with ultraviolet (UV) light. The photoresponse (I_photo/I_dark) behavior of the ZNRs/UNCD PD exhibits a much higher photoresponse (912) than bare ZNRs (229), ZNRs/nanocrystalline diamond (NCD; 518), and ZNRs/microcrystalline diamond (MCD; 325) under illumination at λ=365 nm. A photodetector with UNCD films offers superior stability and a longer lifetime compared with carbon materials and bare ZNRs. The lifetime stability of the ZNRs/UNCD‐based device is about 410 min, which is markedly superior to devices that use bare ZNRs (92 min). The ZNRs/UNCD PD possesses excellent photoresponse properties with improved lifetime and stability; in addition, ZNRs/UNCD‐based UV emitters have great potential for applications such as cathodes in flat‐panel displays and microplasma display devices.     

Synthetic erythropoietic proteins: tuning biological performance by site-specific polymer attachment

Chemical synthesis in combination with precision polymer modification allows the systematic exploration of the effect of protein properties, such as charge and hydrodynamic radius, on potency using defined, homogeneous conjugates. A series of polymer-modified synthetic erythropoiesis proteins were constructed that had a polypeptide chain similar to the amino acid sequence of human erythropoietin but differed significantly in the number and type of attached polymers. The analogs differed in charge from +5 to -26 at neutral pH and varied in molecular weight from 30 to 54 kDa. All were active in an in vitro cell proliferation assay. However, in vivo potency was found to be strongly dependent on overall charge and size. The trends observed in this study may serve as starting points for the construction of more potent synthetic EPO analogs in the future.     

Nanometer Channels and Cages within the Extended Basic Mercurous Cations [(Hg2)3(OH)2]4+ and [(Hg2)2O]2+

The two‐ and three‐dimensional mercurous cations [(Hg₂)₃(OH)₂]⁴⁺ and [(Hg₂)₂O]²⁺ crystallize with channels and cages of roughly 1 nm diameter from aqueous solutions dependent upon the acidity of the solution. Crystal structures were determined, for example, for [Zn(H₂O)₆][(Hg₂)₃(OH)₂](NO₃)₆ (trigonal, space group P321, a = 1183.5(2) pm, c = 534.8(1) pm, Z = 1, R1 = 0.0351 for I₀ > 2σ(I₀)) and for [(Hg₂)₂O][Pb(NO₃)₃]₂ (cubic, space group , a = 1543.1(2) pm, Z = 8, R1 = 0.0534 I₀ > 2σ(I₀)).     

Strong Attraction of Caffeine to the Mercurous Dumbbell in the Salt [Hg2(Caf)2](ClO4)2(H2O)2

Colourless single crystals of the caffeine adduct of mercurous perchlorate dihydrate, [Hg₂(Caf)₂](ClO₄)₂(H₂O)₂, were grown from aqueous solutions of mercurous perchlorate and caffeine by isothermal evaporation at ambient temperature. The crystal structure (monoclinic, P2₁/n, Z = 4, a = 1628.0(2), b = 780.4(1), c = 2229.6(3) pm, β = 99.84(1)°, R₁(all data) = 0.0894) contains [trans‐Caf‐Hg‐Hg‐Caf]²⁺ cations with a Hg‐Hg distance of 250.88(6) pm, Hg‐N (bond) distances of 214.4(6) and 215.1(6) pm and Hg‐Hg‐N angles of 176.9(2) and 165.1(2)°, respectively. These cations are attached via weak Hg‐O contacts to dimers which are further arranged to leave large channels into which one crystal water molecule is included. The second water molecule and the two perchlorate anions are weakly attracted to one Hg atom.     

HPLC separation and quantification of anionic surfactants using an automated on-line ion pair extraction system

Summary Aliphatic anionic surfactants, like alkylsulfonates, alkyl sulfates, -sulfo alkanoic acids and their esters, were separated with respect to their alkyl chain length by high performance liquid chromatography (HPLC) using reversed phase (RP) columns. For sensitive and specific detection of these classes of compounds the HPLC separation was combined with a post-column ion-pair extraction system. The limit of detection is in the range of 3–30 ng. Previously reported detection systems of this kind were modified by changing the inner set-up of the phase separator and the extraction capillary and integrating a purge function, which led to a higher system stability and made automatization possible. In order to optimize the experimental set-up, the influence of the reagent concentration as well as different sizes and materials of the extraction capillary were evaluated. The calibration curve of surfactant concentrations versus fluorescence emission is discussed for sodium decylsulfonate. Since both the electrolyte concentration and the percentage of organic solvents in the mobile phase may adversely affect the detection system, different eluent compositions were tested.This article is part of the planned dissertation of Markus Schoester at the Mathematical Natural Science Faculty of the University of Düsseldorf     

On universal subsets of Banach spaces

We prove that to most of the known hypercyclic operators A on separable Banach spaces there exist compact (compact convex, compact connected) subsets K of E such that each compact (compact convex, compact connected) subset of E can be approximated with respect to Hausdorff's distance by for suitable . Received July 8, 1997, in final form October 17, 1997     

Structure-activity-based design of a synthetic malaria peptide eliciting sporozoite inhibitory antibodies in a virosomal formulation

The circumsporozoite protein (CSP) of Plasmodium falciparum is a leading candidate antigen for inclusion in a malaria subunit vaccine. We describe here the design of a conformationally constrained synthetic peptide, designated UK-39, which has structural and antigenic similarity to the NPNA-repeat region of native CSP. NMR studies on the antigen support the presence of helical turn-like structures within consecutive NPNA motifs in aqueous solution. Intramuscular delivery of UK-39 to mice and rabbits on the surface of reconstituted influenza virosomes elicited high titers of sporozoite crossreactive antibodies. Influenza virus proteins were crucially important for the immunostimulatory activity of the virosome-based antigen delivery system, as a liposomal formulation of UK-39 was not immunogenic. IgG antibodies elicited by UK-39 inhibited invasion of hepatocytes by P. falciparum sporozoites, but not by antigenically distinct P. yoelii sporozoites. Our approach to optimized virosome-formulated synthetic peptide vaccines should be generally applicable for other infectious and noninfectious diseases.