Option pricing in incomplete discrete markets

Various methods of option pricing in discrete time models are discussed. The classical risk minimization method often results in negative prices and a natural modification is proposed. Another method of risk minimization using an inductive procedure as in the Cox-Ross-Rubinstein model is also proposed. The definition of the risk interpreted as the maximum of possible loss is discussed.     

Ligand binding properties of cobalamins

The main goal of the present density functional theory calculations is a comparative study of NO, O₂, ${{\rm NO}_{2}^{-}}$ , and H₂O binding to different forms of cob(II)alamins and cob(III)alamins. The comparison of binding energies of small ligands enables one to draw conclusions regarding the stability of the studied derivatives of cobalamins as well as to define the preferred form of cobalamin for each ligand. Ligands such as NO and O₂ favor cob(II)alamins, while H₂O and ${{\rm NO}_{2}^{-}}$ cob(III)alamins. The obtained results are confronted with available experimental data. Finally, our findings allow one to divide the studied small ligands into two groups: NO and O₂ for which the coordination to cobalamins significantly weakens their internal bonds, and ${{\rm NO}_{2}^{-}}$ and H₂O for which the effect is not observed.     

Multifrequency electron paramagnetic resonance study on deproteinized human bone

Irradiated samples of deproteinized powdered human bone (femur) have been examined by electron paramagnetic resonance (EPR) spectroscopy in X, Q and W bands. In the bone powder sample only one type of CO2- radical ion is stabilized in the hydroxyapatite structure in contrast to powdered human tooth enamel, a material also containing hydroxyapatite, widely used for EPR dosimetry and in which a few radicals are stable at room temperature. It is suggested that the use of deproteinized bone for EPR dosimetry could improve the accuracy of dose determination.     

Surface activity of commercial food grade modified starches

An attempt to quantitative evaluation of the functionality of food grade chemically modified starches in the emulsion systems by estimation of their surface activity as well as the capability of thickening food products was the main purpose of this present work. It was stated that chemically modified starches reveal higher surface activity at air/water and toluene/water interfaces in comparison to the native starch. The increase of the degree of substitution of polar carboxyl groups as well as rather non-polar acetyl ones results in an enhance of surface activity. Starch sodium octenylsuccinate stands out from other investigated starches, in its excellent capability of lowering surface and interfacial tension. Cross-linked starches reveal excellent stabilisation activity at a pH range of 5.5–7.0 but their surface activity is lower than those of other modified starches. Acetylated starch as well as starch sodium octenylsuccinate reveal satisfactory thickening capability up to pH 4.5 and moreover their surface activity (especially of E 1450) allows us to recommend them as functional constituents of food emulsions. Low thickening capability of oxidised starches rather excluded these derivatives from the group of potential functional additives for food emulsions.     

Electron paramagnetic resonance (EPR) study of γ-radiation-induced radicals in 1,3,5-trithiane and its derivatives

Radicals formed in γ-irradiated 1,3,5-trithiane (TT) and its three derivatives, α- and β-2,4,6-trimethyl-1,3,5-trithiane (α-TMT and β-TMT), and 2,4,6-trimethyl-2,4,6-triphenyl-1,3,5-trithiane (TMTPT), were studied by the electron paramagnetic resonance (EPR) method in the solid state. The sulfur radical cations (>S^+•) were identified in all compounds at 77 K. In TT and its two derivatives, α-TMT and β-TMT, the >S^+• decay via deprotonation-forming C-centered radicals. Further increase of temperature up to 293 K results in the appearance of thiyl-type radicals (RS^•). In TMTPT, the >S^+• are stable up to 250 K. They formed the intermolecularly three-electron-bonded dimeric radical cations (S∴S)⁺ while RS^• radicals were not observed. Some of the radical assignments and their EPR parameters (g and a hyperfine splittings) obtained support from the DFT calculations.     

Ultrasound‐assisted solid‐phase extraction coupled with photodiode‐array and fluorescence detection for chemotaxonomy of isoflavone phytoestrogens in Trifolium L. (Clover) species

Detailed chemotaxonomic studies were undertaken to establish the qualitative profile and real amounts of the pharmacologically active isoflavone aglycones genistein, daidzein, formononetin, and biochanin A in aerial parts of thirteen Trifolium L. (clover) species, native to Poland. A newly elaborated micropreparative technique – SPE – on BakerBond octadecyl, cyclohexyl, and phenyl cartridges was used in combination with ultrasound‐assisted extraction for isolation of isoflavone aglycones from hydrolyzed samples. The effectiveness of all three SPE sorbents in the purification of plant extracts was compared and very high recoveries (>96%) were documented for four isoflavones. Classical photodiode‐array and very sensitive fluorescence detection, coupled with reversed‐phase high‐performance liquid chromatography (RP‐HPLC), were employed to obtain the most reliable qualitative and quantitative results. Chemotaxonomic differences combined with flower color variability were demonstrated within thirteen clover species. Concentration levels of particular isoflavones in ten Trifolium species possessing flowers with white, pink, or purple‐red corolla ranged from ∼︁3 to ∼︁3300 μg/g dry weight, while in three yellow flowering clovers (T. aureum, T. dubium, and T. campestre) isoflavone compounds have not been detected at all. RSD values, determined for intra‐ and inter‐day precision of the quantitative results, were not higher than 6.2% and 7.1%, respectively.     

Light-driven OR and XOR programmable chemical logic gates

Photoelectrodes made of nanocrystalline titanium dioxide modified with various pentacyanoferrates exhibit unique photoelectrochemical properties; photocurrent direction can be switched from anodic to cathodic and vice versa upon changes in photoelectrode potential and incident light wavelength (PhotoElectrochemical Photocurrent Switching, PEPS effect). At certain potentials, anodic photocurrent generated upon UV irradiation has the same intensity as the cathodic photocurrent generated upon visible irradiation. Under these conditions, simultaneous irradiation with UV and visible light results in compensation of anodic and cathodic photocurrents, and zero net photocurrent is observed. This process can be used for construction of unique light-driven chemical logic gates.     

Polyester-based Copolymers for Biomaterials Fabrication

Summary: Results on synthesis of poly(3-hydroxybutyrate)s possessing one or two hydroxyl groups at one terminus of the chain and carboxylic group at the other chain end are reported. These polymers were further functionalised via transesterification with dimethyl H-phosphonate thus incorporating a reactive/biodegradable center in the polyester backbone. Block/star-like copolymers composed of hydrophilic PEG and hydrophobic poly(3-hydroxybutyrate) segments linked by phosphoester moiety were also obtained. Chemical structure and composition of the reaction products were analysed applying different spectroscopic techniques (¹H, and ³¹P NMR, IR and ESI-MS) and size exclusion chromatography was applied to describe molecular weight averages and distribution.     

Novel C60 Fullerenol-Gentamicin Conjugate–Physicochemical Characterization and Evaluation of Antibacterial and Cytotoxic Properties

This study aimed to develop, characterize, and evaluate antibacterial and cytotoxic properties of novel fullerene derivative composed of C₆₀ fullerenol and standard aminoglycoside antibiotic–gentamicin (C₆₀ fullerenol-gentamicin conjugate). The successful introduction of gentamicin to fullerenol was confirmed by X-ray photoelectron spectroscopy which together with thermogravimetric and spectroscopic analysis revealing the formula of the composition as C₆₀(OH)₁₂(GLYMO)₁₁(Gentamicin)_0.8. The dynamic light scattering (DLS) revealed that conjugate possessed ability to form agglomerates in water (size around 115 nm), while Zeta potential measurements demonstrated that such agglomerates possessed neutral character. In vitro biological assays indicated that obtained C₆₀ fullerenol-gentamicin conjugate possessed the same antibacterial activity as standard gentamicin against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli, which proves that combination of fullerenol with gentamicin does not cause the loss of antibacterial activity of antibiotic. Moreover, cytotoxicity assessment demonstrated that obtained fullerenol-gentamicin derivative did not decrease viability of normal human fibroblasts (model eukaryotic cells) compared to control fibroblasts. Thus, taking into account all of the results, it can be stated that this research presents effective method to fabricate C₆₀ fullerenol-gentamicin conjugate and proves that such derivative possesses desired antibacterial properties without unfavorable cytotoxic effects towards eukaryotic cells in vitro. These promising preliminary results indicate that obtained C₆₀ fullerenol-gentamicin conjugate could have biomedical potential. It may be presumed that obtained fullerenol may be used as an effective carrier for antibiotic, and developed fullerenol-gentamicin conjugate may be apply locally (i.e., at the wound site). Moreover, in future we will evaluate possibility of its applications in inter alia tissue engineering, namely as a component of wound dressings and implantable biomaterials.     

Mechanistic information on the copper-catalysed autoxidation of mercaptosuccinic acid in aqueous solution

Copper(II) ions react rapidly with sulfur from thiol groups, forming two distinct, intensely absorbing, short-lived intermediates, which decompose in a subsequent redox reaction to produce reduced copper and disulfides. In this study we report the results of a mechanistic study on the reaction between mercaptosuccinic acid, HO(2)CCH(2)CH(SH)CO(2)H, and Cu(2+)(aq) and [Cu(tren)H(2)O](2+), tren = tris(2-aminoethyl)amine. Spectroscopic and kinetic data indicate that in the presence of an excess of thiol, at least two distinct complexes are formed, with very different decomposition rate constants and an absorption maximum at 346 nm. Upon addition of thiol to [Cu(tren)H(2)O](2+)(1:1), a transient with a maximum at 380 nm appears, whereas in an excess of thiol this complex decomposes and again the 346 nm band is observed. The use of [Cu(tren)H(2)O](2+) enables to study the reaction of thiol with copper also in alkaline solution, where the rate of the overall process is slowed down greatly. The reactions were studied in detail, including the effect of dioxygen, and a possible reaction mechanism for the catalysed autoxidation process is proposed and discussed in reference to available literature data.