Semi-implicit complementary volume scheme for solving level set like equations in image processing and curve evolution

Summary. We introduce linear semi-implicit complementary volume numerical scheme for solving level set like nonlinear degenerate diffusion equations arising in image processing and curve evolution problems. We study discretization of image selective smoothing equation of mean curvature flow type given by Alvarez, Lions and Morel ([3]). Solution of the level set equation of Osher and Sethian ([26], \[30]) is also included in the study. We prove and estimates for the proposed scheme and give existence of its (generalized) solution in every discrete time-scale step. Efficiency of the scheme is given by its linearity and stability. Preconditioned iterative solvers are used for computing arising linear systems. We present computational results related to image processing and plane curve evolution. Received April 25, 2000 / Revised version received June 11, 2001 / Published online November 15, 2001     

Composting and biodegradation of thermally processed feather keratin polymer

Proteins obtained from agricultural sources represent a unique feedstock from which to prepare thermally processable polymers. In this study, thermally processed feather keratin films were composted with three-month-old compost inoculum in self-heating laboratory composters for 30 days and temperature and carbon dioxide development monitored. About 24% of the available carbon in the feather keratin polymer (FKP) was metabolized in this time and this may not be high enough for some applications. Degradation of the feather keratin polymers was observed within 10 days with concurrent molecular weight reduction measured using FT-IR. Visual inspection of the polymers also showed destruction of the films. A change in crystallinity was observed in DSC analysis and some degradation processes could be inferred from this as well.     

Excess enthalpies of aqueous ternary solutions of urea and polyols at 25°C

The heats of dilution of nine ternary solutions of urea and polyols have been determined at 25°C. Excess enthalpies and their virial coefficients h _xy have been evaluated and compared with the data reported in the literature for mono- and polyfunctional alcohols and other oxygenated nonelectrolytes. The group additivity approach of Savage and Wood was applied and the contributions to the enthalpy coefficients, due to the water mediated interactions between urea and the functional groups –CH₂–, –OH, and –O– were determined. On the other hand, by using empirical combination rules among the cross- and self-enthalpic interaction coefficients it is possible to emphasize the large differences in the behavior (even in the presence of urea) of the polyols (and in particular of cyclitols) and of saccharides.     

Oesophageal cancer treated by photodynamic therapy alone or followed by radiation therapy

Photodynamic therapy (PDT) with porphyrins and red light is receiving increasing attention in the management of malignant tumours. At present PDT is primarily indicated for the treatment of superficial or early-stage lesions. At the Department of Radiotherapy and the First Institute of Surgery in Padova (Italy) more than 150 cases of tumours of different types have been treated using this technique. This paper briefly describes 21 cases of superficial oesophageal cancer. A complete response was observed in 11 of 21 cases. Radiation therapy appeared to be very effective as a salvage treatment of non-response patients.     

Reaction between quinone and thiazolidine. A study on the formation mechanism of new antiproliferative quinolindiones

Reaction between quinolinquinone and thiazolidine in basic medium was investigated. 2-Arylthiazolidine-4-carboxylic acid ethyl esters undergo two different cleavages in basic medium, yielding the 1-aryl-2-azadiene and a thiolic species. In the presence of quinolinquinone, the isomeric 1-aryl-3-ethoxycarbonyl-pyridoisoquinolin-5,10-diones and 3-amino-3-ethoxycarbonyl-dihydrothienoquinolin-4,9-diones are formed by a hetero-Diels-Alder reaction and 1,4-Michael addition reaction, respectively. A mechanism for the formation of the reaction products is presented.     

Improved high-performance liquid chromatographic method for the determination of coenzyme Q10 in plasma.

Coenzyme (Co) Q10 was dissociated from lipoproteins in plasma by treatment with methanol and extraction with n-hexane. Subsequent clean-up on silica gel and C18 solid-phase extraction cartridges with complete recovery (99 +/- 1.2%) produced a clean extract. High-performance liquid chromatographic (HPLC) separation was performed on a C18 reversed-phase column. Three simple, rapid procedures are presented: HPLC with final UV (275 nm) detection, a microanalysis utilizing a three-electrode electrochemical detector and a microanalysis with column-switching HPLC and electrochemical detection. The methods correlate very well with classical ethanol-n-hexane extraction with UV detection. The identity and purity of the Co Q10 peak were investigated and the resulting methods were concluded to be suitable for total plasma Co Q10 determination. The average level in healthy subjects was 0.80 +/- 0.20 mg/l; the minimum detectable Co Q10 plasma level was 0.05 and 0.005 mg/l for UV and electrochemical detection, respectively. The methods were applied to many samples and the plasma Co Q10 reference values for healthy subjects, athletes, hyperthyroid, hypothyroid and hypercholesterolaemic patients are given.     

Understanding the role of stereoelectronic effects in determining collagen stability. 2. A quantum mechanical/molecular mechanical study of (Proline-Proline-Glycine)(n) polypeptides

The importance of vicinal and long-range interresidue effects in determining the stability of the collagen triple helix has been investigated by quantum mechanical (QM) and molecular mechanical (MM) computations on suitable model polypeptides, taking into account solvent effects by the polarizable continuum model (PCM). At the QM level, the PII conformation corresponds to an energy minimum for pentapeptide analogues incorporating the sequence Gly-Pro-Pro-Gly, irrespective of the down or up puckering of the pyrrolidine ring. However, our computations indicate that the alternation of down and up prolines characterizing collagen and collagen-like peptides is not due to an intrinsic preference of the Pro-Pro-Gly sequence. This result is confirmed by MM computations of longer polypeptides. Next, MM computations on model triple helices show that a better packing is obtained for specific values of backbone dihedrals, which, in turn, favor the alternation of down and up prolines along each chain.     

The temperature-induced denaturation of small globular proteins as a first-order phase transition of ‘crystal molecules’

A general feature of temperature-induced reversible denaturation of small globular proteins is its all-or-none character. This strong cooperativity leads to think that protein molecules, possessing only two accessible thermodynamic states, the native and the denatured one, resemble ‘crystal molecules’ that melt at raising temperature. An analysis, grounded on mean field theory, allows to conclude that the two-state transition is a first-order phase transition. The implication of this conclusion are briefly discussed.     

The hydrophobic effect in aqueous solutions of nonelectrolytes. I. Self-interactions of alkylureas

In order to clarify some aspects of the hydrophobic interactions, the enthalpies of dilution of monoethylurea, 1,3-dimethylurea, and 1,3-diethylurea have been determined calorimetrically at 25°C. The calorimetric data, expressed in terms of excess enthalpy, permit the evaluation of the pair and triplet interaction coefficients. The analyses of these and of the analogous coefficientsg _xx andg _xxx, derived from osmotic data, indicate a driving force favorable to the interactions among the hydrated solute molecules. Nevertheless, the positive values of theh _xx andh _xxx coefficients seem to suggest that the source of the effect is a rearrangement of the water molecules rather than a direct association of the solute molecules. There are evidences of a strict correlation between the enthalpic and the entropic effects. Preliminary data were presented at the International Conferences on Chemical Thermodynamics at Baden (1973) and Montpellier (1975). The experimental part was carried out at the Istituto Chimico of the University of Trieste. To whom correspondence should be addressed.