Randomized on-line algorithms and lower bounds for computing large independent sets in disk graphs

We study the on-line version of the maximum independent set problem, for the case of disk graphs which are graphs resulting from intersections of disks on the plane. In particular, we investigate whether randomization can be used to break known lower bounds for deterministic on-line independent set algorithms and present new upper and lower bounds.     

Efficient guanylation of N,N-difunctionalized polyamines at the secondary amino functions

Treatment of N^α,N^ω-ditritylated linear and aromatic polyamines and of polyamine conjugates of the alkaloid kukoamine A (KukA) type with N,N′-bis(tert-butoxycarbonyl)thiourea in the presence of Mukaiyama’s reagent produced high yields of derivatives guanylated at the secondary amino functions.     

Efficient syntheses of 5-aminoalkyl-1h-tetrazoles and of polyamines incorporating tetrazole rings

Linear N(omega)-tritylated omega-amino thiobenzylamides and N(alpha),N(omega)-ditritylated polyamino mono- or bisthioamides were efficiently converted to the corresponding tetrazole derivatives upon treatment with azidotrimethylsilane under Mitsunobu reaction conditions. [reaction: see text]     

Low energy π-π resonances in the Veneziano model

We attempt to impose elastic unitarity on the forward π-π scattering using the Veneziano Amplitude together with a crossing symmetric subtraction term as an input. TheN/D method is used and thep, ? mesons are interpreted as CDD poles. The self consistency requirement led to the evalutation of the low energy parameters and theS andP-wave phase shifts. The values of the scattering lengths obtained area ₀ ⁰ =0.084m _π ^?1 ,a ₂ ⁰ =?0.024m _π ^?1 ,a ₁ ¹ =0.047m _π ^?3 .     

Effects of the inclusive dipole-pomeron to exclusive processes

The consequences of the inclusive dipole-Pomeron for the exclusive processes are investigated. In the weak coupling limit a two component picture for the production mechanism is obtained and self-consistency of the inclusive Pomeron dipole is found.     

N-Arylation of a hindered indoline as a route to 2-(2-methyl-1-(4-oxo-3,4-dihydrophthalazin-1-yl)-1H-indol-3-yl)acetic acid derivatives

A convenient synthesis of 2-(2-methyl-1-(4-oxo-3,4-dihydrophthalazin-1-yl)-1H-indol-3-yl)acetic acid derivatives is described using a microwave-promoted multi-step S_NAr reaction. The desired products were found to exhibit atropisomerism.     

Tunable reagents for multi-functional bioconjugation: reversible or permanent chemical modification of proteins and peptides by control of maleimide hydrolysis

Controlling maleimide hydrolysis allows the modular construction of bromomaleimide-mediated bioconjugates which are either stable or cleavable in an aqueous, thiol-mediated reducing environment. The application of this methodology to reversible protein biotinylation, the irreversible labeling of peptide disulfide bonds and the assembly of stable, fluorescein-labelled glycoprotein mimics is described.     

Significant modification of the I(-)3 Lewis base character in the β-cyclodextrin polyiodide inclusion complex with Co2+ ion: an FT-Raman investigation

The β-cyclodextrin (β-CD) polyiodide inclusion complex (β-CD)(2)·Co(0.5)·I(7)·21H(2)O has been synthesized, characterized and further investigated via FT-Raman spectroscopy in the temperature range of 30-120°C. The experimental results point to the coexistence of I(-)(7) units (I(2)·I(-)(3)·I(2)) that seem not to interact with the Co(2+) ions and I(-)(7) units that display such interactions. The former units exhibit a disorder-order transition of both their I(2) molecules above 60°C due to a symmetric charge-transfer interaction with the central I(-)(3) [I(2)←I(-)(3)→I(2)], whereas in the latter units only one of the two I(2) molecules becomes well-ordered above 30°C. The other I(2) molecule remains disordered presenting no charge-transfer phenomena. The Co(2+) ion induces a considerable asymmetry on the geometry of the I(-)(3) anion and a significant modification of its Lewis base character. Complementary dielectric measurements suggest no important involvement of H···I contacts in the observed modification of the I(-)(3) electron-transfer properties.     

Pseudo-potentiostatic electrolysis by potential buffering induced by the oxygen evolution reaction

A new approach is proposed in order to perform electrochemical oxidation of organics by working under galvanostatic conditions with the potential ‘buffered’ by the competing side reaction of oxygen evolution (OER). According to this process the working potential is fixed by the nature of electrode material and is buffered during organics oxidation by the side reaction of OER. This principle has been used for the selective oxidation of some model organic compounds on Ti/IrO₂ anode.     

Sonodegradation of 17α-ethynylestradiol in environmentally relevant matrices: laboratory-scale kinetic studies

The sonochemical degradation of 17α-ethynylestradiol (EE2) in secondary treated effluents was investigated. Ultrasound irradiation was provided by a horn-type sonicator operating at 80 kHz. The effect of various operating conditions such as estrogen concentration (25-160 μg/L), power density (18-46 W/L), liquid bulk temperature (15-60 °C), gas sparging (air, oxygen, and helium), solution pH (3 and 7.8), as well as the addition of radical promoters (hydrogen peroxide) or catalysts (TiO₂ and Fe²⁺) on degradation kinetics was evaluated. Changes in estrogen concentration were followed by high performance liquid chromatography and the yeast estrogen screening (YES) assay. EE2 degradation in the range 25-110 μg/L follows first order kinetics in regard to its concentration, while lower order kinetics occur at higher concentrations. The reaction rate increases linearly with applied power and decreases exponentially with temperature at the conditions in question. Continuous sparging of air or oxygen has little effect on the kinetics relative to air-equilibrated conditions, while helium has a marginally positive effect. The inorganic and organic contents of the wastewater matrix appear to promote degradation at inherent conditions in comparison to experiments in ultrapure water. Nevertheless, the addition of H₂O₂ (8.6 and 86 mg/L), Fe²⁺ (2.5-25 mg/L) or TiO₂ (50-2000 mg/L) has no or, in some cases, adverse effect on kinetics.