Hilbert algebras as implicative partial semilattices

The infimum of elements a and b of a Hilbert algebra are said to be the compatible meet of a and b, if the elements a and b are compatible in a certain strict sense. The subject of the paper will be Hilbert algebras equipped with the compatible meet operation, which normally is partial. A partial lower semilattice is shown to be a reduct of such an expanded Hilbert algebra i ?both algebras have the same ?lters.An expanded Hilbert algebra is actually an implicative partial semilattice (i.e., a relative subalgebra of an implicative semilattice),and conversely.The implication in an implicative partial semilattice is characterised in terms of ?lters of the underlying partial semilattice.     

Analysis of primary aliphatic short-chain monoamines by LC in water samples

Several derivatization procedures with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) were compared for a rapid analysis of primary aliphatic short-chain monoamines in water samples by HPLC using a LiChorospher analytical separation column (100RP₁₈ mm i.d., 5 μm). Both the solution and the solid-support assisted off-line derivatization on C₁₈ SPE cartridges were inadequate options because of beginning degradation processes of the instable isoindol derivatives during their transfer to the analytical column. This problem was precluded with the on-column or solid-support assisted on-line derivatization. In the last mentioned procedure, the derivatization took place in a Hypersil C₁₈ precolumn ( mm i.d., 30 μm) connected with an additional preconcentration step resulting in better detection limits (0.002-0.040 μg ml⁻¹ requiring only 150 μl of water sample) than in the on-column procedure (0.08-0.16 μg ml⁻¹). The improved sample handling, the better control of parameters affecting reaction rates, the fully automation of this method with only 10 min analysis time for each sample are further advantageous. The potential of the solid-support assisted on-line derivatization was outlined and applied to water samples from several sources. Recovery values near 100% were obtained.     

On the reactivity of benzidinesulfonic acids and their applications in analysis: Reaction of cupric salts with o-benzidinemonosulfonic acid in presence of alkali thiocyanate

In the present work a new method for the detection of coppcr(II) is described. It is based on the reaction of this ion with the alkali salts of o-benzidinemonosulfonic acid, alkali thiocyanate being present. The sensitivity of this test is $\text{1}\text{500,000}$ (l0^-5.7); it ia specific for the Cu⁺² ion and can also be used to distinguish quickly the above-mentioned acid from the benzidine o-o'-disulfonic and benzidine m-m' '-disulfonic acids. It is believed that the mechanism of the reaction can be explained by an oxidation process.     

Macrocyclization of bis-indole quinolines for selective stabilization of G-quadruplex DNA structures

The recognition of G-quadruplex (G4) DNA structures as important regulatory elements in biological mechanisms, and the connection between G4s and the evolvement of different diseases, has sparked interest in developing small organic molecules targeting G4s. However, such compounds often lack drug-like properties and selectivity. Here, we describe the design and synthesis of a novel class of macrocyclic bis-indole quinolines based on their non-macrocyclic lead compounds. The effects of the macrocyclization on the ability to interact with G4 DNA structures were investigated using biophysical assays and molecular dynamic simulations. Overall, this revealed compounds with potent abilities to interact with and stabilize G4 structures and a clear selectivity for both G4 DNA over dsDNA and for parallel/hybrid G4 topologies, which could be attributed to the macrocyclic structure. Moreover, we obtained knowledge about the structure–activity relationship of importance for the macrocyclic design and how structural modifications could be made to construct improved macrocyclic compounds. Thus, the macrocyclization of G4 ligands can serve as a basis for the optimization of research tools to study G4 biology and potential therapeutics targeting G4-related diseases.

Macrocyclization improves the selectivity, affinity, and ability to stabilize G4 DNA structures.     

Dominating Functions and Graphs

A graph is called dominating if its vertices can be labelledwith integers in such a way that for every function : thegraph contains a ray whose sequence of labels eventually exceeds. We obtain a characterization of these graphs by producinga small family of dominating graphs with the property that everydominating graph must contain some member of the family.     

Reaping Numbers of Boolean Algebras

A subset A of a Boolean algebra B is said to be (n,m)-reapedif there is a partition of unity p B of size n such that |{b p:b a 0}| m for all a A. The reaping number r_n,m (B) ofa Boolean algebra B is the minimum cardinality of a set A B\{0}which cannot be (n,m)-reaped. It is shown that for each n, thereis a Boolean algebra B such that r_n+1,2(B) r_n,2(B). Also, {r_n,m(B):mn } consists of at most two consecutive cardinals. The existenceof a Boolean algebra B such that r_n,m (B) r_n',m' (B) is equivalentto a statement in finite combinatorics which is also discussed.     

Simultaneous determination of chromium(III) and chromium(VI) in aqueous solutions by ion chromatography and chemiluminescence detection.

A method for the simultaneous determination of chromium(iii) and chromium(vi) in a flow system based on chemiluminescence was developed. A Dionex cation-exchange guard column was used to separate chromium(iii) from chromium(vi), and chromium(vi) was reduced by potassium sulfite, whereupon both species were detected by use of the luminol-hydrogen peroxide chemiluminescence system. Linear calibration for both species was established over the concentration range 1-1000 micrograms l-1. The precision at the 20 micrograms l-1 level was 3.5% for chromium(iii) and 3.3% for chromium(vi), respectively. The detection limit was 0.5 micrograms l-1 for both species. Data were in agreement with Zeeman-effect background corrected atomic absorption spectrometry measurements.     

Novel radial oligothienyl silanes

A series of thiophene-based homologues with a silicon core surrounded by mono-, bi-, terthiophene, and their derivatives with alkylsilyl linkages has been prepared using hydrosilylation and Stille coupling methods.