Study of the degradation of gelatin in paper upon aging using aqueous size-exclusion chromatography

We studied the aging behaviour of gelatin used to size paper. Thus far, research on the aging of paper has largely ignored the sizing agent. Degradation of the protein was characterised and the impact of paper components, such as cellulose, and aluminium potassium sulphate was evaluated. Whatman No. 1 filter papers sized with two types of gelatins (A and B) were prepared as model samples. Commercially sized modern papers (Arches) were also studied in order to compare laboratory samples with real artist papers. Both types of papers were artificially aged (80 °C, 50% relative humidity for 35 and 94 days). Historic papers were included in the study in order to compare artificially aged with naturally aged gelatin. The aqueous extracts from the papers were characterised by aqueous size-exclusion chromatography (SEC) using four PL-Aquagel-OH columns and UV photodiode array detection at 220, 254 and 280 nm. Results showed that gelatin undergoes hydrolysis upon aging, type A gelatin showing a faster degradation rate than type B. The result was an increase in the lower-molar-mass fractions, under 50 000 g mol⁻¹, and especially in a characteristic fraction with a peak molecular mass (M_p) of 14 000 g mol⁻¹. A significant decrease in the extraction yields of -, β- and γ-chains occurred after aging. This was attributed to crosslinking, leading to the formation of less-soluble polypeptides with very high molar mass (>800 000 g mol⁻¹). Less than 10% alum had no impact on the degradation rate; higher alum contents accelerated hydrolysis reactions.     

Crystal Structure of [Co(NH3)5NO3](NO3)(PF6)?·?1.5H2O and the Vibrational Bands of its Normal and 15NO3-Enriched Cation

The crystal structure of [Co(NH₃)₅NO₃](NO₃)(PF₆) ·1.5 H₂O was studied by X-ray diffraction methods in order to obtain the unknown molecular structure of the [Co(NH₃)₅NO₃]²⁺ cation . The substance crystallizes in the monoclinic system, space group C2/m, with a = 18.6231(6) ?, b = 7.8757(3) ?, c = 9.6434(3) ? and β = 95.484(2)°. An infrared and Raman study of the bromide salt was also performed and the spectra interpreted with the aid of ¹⁴NO₃/¹⁵NO₃ isotopic replacement and quantum chemistry calculations. E.L. Varetti — Member of the Carrera del Investigador Científico, CONICET, R. Argentina     

Coordination Mode and Kinetic Behavior of the Tetracarbonatozirconate Ion

The behavior of [Zr(CO₃)₄]⁴⁻ complex in solution is studied by determining the coordination mode of the carbonato ligands and the kinetic law of the equilibrium between free and complexed carbonates. Raman polarization and dynamic ¹³C-NMR experiments show that complexed carbonates are bidentate. Magnetization-transfer experiments give the values of pseudo-first-order rate constants for the equilibrium with no net chemical transformation. The treatment of these parameters suggests a second-order rate law. As no solvent effect is noticed, an associative mechanism of ligand exchange is proposed.     

Charged silsesquioxane used as a vehicle for gold nanoparticles to perform the synthesis of catalyst xerogels

The water soluble charged silsesquioxane that contains the bridged 1,4-diazoniabicyclo[2.2.2]octane chloride group, was used as stabilizing agent and size controller in the synthesis of gold nanoparticles smaller than 15?nm in aqueous medium. The gold nanoparticle dispersion was converted in solid powder form by evaporation. This powder presented organized structure imposed by the presence of charged organic group, similar to organized structure already observed for pure silsesquioxane. The gold nanoparticles in solid powder form presented high storage stability for several months, at ambient conditions, and can be completely redispersed in water again. After redispersion, the optical properties of gold nanoparticles, observed by ultra-violet and visible spectroscopy, and their morphological characteristics, investigated by transmission electron microscopy, are preserved. The gold nanoparticle aqueous dispersion was used as a vehicle of nanoparticles in the synthesis of sol?Cgel silica based hybrid material. This xerogel was characterized by N₂ adsorption?Cdesorption isotherms, showing 260?m²g^?1, and it was applied in a satisfactory way as catalyst for p-nitrophenol reduction to p-aminephenol.     

A mathematical model of pricing in a large system of cash bonds

The purpose of this paper is to give a mathematical model to generalize the classical approach of compound interest and to overcome the time structure problem of the interest rates. We introduce a suitable stochastic process called the ‘gauge’ process such that its product with the value of any security is assumed to be a martingale in an appropriate probability space. The framework of this model gives a stochastic actualization formula for the pricing of general securities with options and includes Black and Schole's formula without using arbitrage arguments. Emphasis has been placed on numerical calculation.     

Individual transferable vessel quotas and efficient restructuring of the primary harvesting sector

Over the last three decades most of the world's fisheries have been subject to management programs that have tried to limit the use of key fishing inputs. Inevitably, these restrictions have proven ineffective at preventing rent dissipation and stock depletion. More noteworthy is that fishers have subverted the intentions of these restrictions by adjusting the primary harvesting technology. This has led to an inefficient industrial structure characterized by capital stuffing on the part of each vessel, excess employment, an inefficient mix of vessels in the fleet, and too many vessels altogether.A promising means of encouraging more efficient primary harvesting is the individual transferable vessel quota that allocates a given catch to each vessel, thereby giving an incentive to catch the quota at least cost. This paper examines efficiency gains and potential industry restructuring from the introduction of an ITVQ into a fishery that was previously subject to input restrictions.Using data from the British Columbia salmon fishery, this paper estimates restricted cost functions for each of four different vessel types and simulates the operations of a market for ITVQs. The demand for quota comes from individual vessels and is found by differentiating the cost function with respect to the shadow price of quota. The market for quota is in equilibrium when the total demand for quota is equal to the fixed supply of quota set by the government. This implicitly defines the equilibrium quota rental price. Results show that the ITVQ could generate unit rental prices for quota between 31 and 93 cents per pound (18–53% of the average landed price).Using this simulated price, each vessel's costminimizing strategy is defined and both low cost vessels (those that will buy quota) and high cost vessels (those that will sell quota and exit the fishery) are identified. Quota trades between the two groups result in efficiency gains. These include reduced capital stuffing, exit of less efficient vessel types, attainment of economies of scale, and an efficient composition of vessel types in the fleet. In aggregate these gains lead to an estimate of annual resource rent that is approximately equal to one third of the value of the catch.     

Dynamical Stark Effect in the nu(2)/nu(4) Vibrational Polyad of SiH(4): Theory and Observation

We report a theoretical and experimental investigation of the dynamical Stark effect in a tetrahedral molecule, silane (SiH(4)). We use a tetrahedral formalism and Floquet theory to calculate the absorption spectra for the molecule dressed by an intense nonresonant pulsed laser. Experimentally, the dynamical Stark effect is observed for transitions of the nu(2)/nu(4) vibrational polyad of SiH(4) by means of nanosecond diode laser absorption spectroscopy and a Nd:YAG laser excitation. Copyright 2000 Academic Press.