Two Enhanced Fourth Order Diffusion Models for Image Denoising

This paper presents two new higher order diffusion models for removing noise from images. The models employ fractional derivatives and are modifications of an existing fourth order partial differential equation (PDE) model which was developed by You and Kaveh as a generalization of the well-known second order Perona-Malik equation. The modifications serve to cure the ill-posedness of the You-Kaveh model without sacrificing performance. Also proposed in this paper is a simple smoothing technique which can be used in numerical experiments to improve denoising and reduce processing time. Numerical experiments are shown for comparison.     

Environmentally Benign Oxidation of Alkylphenols to p-Benzoquinones: A Comparative Study of Various Ti-Containing Catalysts

Catalytic properties of Ti-containing porous solids were compared in the oxidation of 2,3,6-trimethylphenol (TMP) with H₂O₂ to produce 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate). Mesoporous titanium–silicates with di(oligo)nuclear Ti centers, metal–organic framework MIL-125 and amorphous TiO₂ demonstrated 100 % selectivity toward TMBQ. Titanium–silicates prepared by evaporation-induced self-assembly revealed superior performance in terms of product yield and catalyst reusability.

     

Development of orally active oxytocin antagonists: studies on 1-(1-[4-[1-(2-methyl-1-oxidopyridin-3-ylmethyl)piperidin-4-yloxy]-2- methoxybenzoyl]piperidin-4-yl)-1,4-dihydrobenz[d][1,3]oxazin-2-one (L-372,662) and related pyridines

The previously reported oxytocin antagonist L-371,257 (2) has been modified at its acetylpiperidine terminus to incorporate various pyridine N-oxide groups. This modification has led to the identification of compounds with improved pharmacokinetics and excellent oral bioavailability. The pyridine N-oxide series is exemplified by L-372,662 (30), which possessed good potency in vitro (Ki = 4.1 nM, cloned human oxytocin receptor) and in vivo (intravenous AD50 = 0.71 mg/kg in the rat), excellent oral bioavailability (90% in the rat, 96% in the dog), good aqueous solubility (>8.5 mg/mL at pH 5.2) which should facilitate formulation for iv administration, and excellent selectivity against the human arginine vasopressin receptors. Incorporation of a 5-fluoro substituent on the central benzoyl ring of this class of oxytocin antagonists enhanced in vitro and in vivo potency but was detrimental to the pharmacokinetic profiles of these compounds. Although lipophilic substitution around the pyridine ring of compound 30 gave higher affinity in vitro, such substituents were a metabolic liability and caused shortfalls in vivo. Two approaches to prevent this metabolism, addition of a cyclic constraint and incorporation of trifluoromethyl groups, were examined. The former approach was ineffective because of metabolic hydroxylation on the constrained ring system, whereas the latter showed improvement in plasma pharmacokinetics in some cases.     

The use of nitride intermediates in the preparation of metals. A study of the reduction of Nb2O5 with NH3

A kinetics study of the reduction of Nb₂O₅ with NH₃ was conducted at 600° to 1300°C, using vertical fixed-bed, flow-through reactors, with the goal of using the nitride as an interme-diate in the preparation of niobium (columbium) metal via a thermal decomposition step. The effects of reactor materials (stainless steel, nickel, molybdenum, graphite, alumina, and Vycor) upon ammonia reactivity toward Nb₂O₅ were investigated. At low temperatures, the metal reactor systems were more catalytically reactive, yielding faster rates of reac-tion and a greater degree of nitride conversion, whereas at high temperatures, the non-metal reactor systems performed better. In general, the initial reaction rate-temperature data exhibited a maximum, associated with oxynitride formation, near 700°C for the metal reactor systems and 800° to 900°C for the nonmetal reactor systems, followed by a mini-mum, associated with NbO₂ formation, at 800° to 850°C for the metal reactor systems and 950° to 1000°C for the nonmetal reactor systems where NbN formation commences. A sec-ond maximum, associated with the hexagonal NbN phase, occurred at 1200°C. The ranges of activation energies for these regions were from 15 to 30 kcal/mole for region I, 8 to 22 kcal/mole for region II, and 10 to 22 kcal/mole for region III.     

Thermal activated (thermal) battery technology: Part II. Molten salt electrolytes

This article gives an overview of the important properties and design characteristics of electrolyte used in thermally activated (thermal) batteries. The basic physical properties of the main compositions are reviewed. The properties of electrolytes such as melting point, ionic conductivity, surface tension, density, thermal characteristics, and moisture sensitivity were analyzed in relation with the functioning of the batteries. Solubility data of alkali metals, sulphides, and oxides were compiled and analyzed. The important parameters of separator pellets are discussed in terms of both electrical and mechanical properties as they pertain to thermal-battery design and functioning. A number of lower-melting electrolytes are presented along with key physical properties for possible use in applications requiring lower operating temperatures such as borehole power supplies.     

Occupational medicine in Canada and Poland in the 1990s

The protocol describes (i) methods for the investigation of neuropeptide catabolism in the central nervous system (CNS), (ii) the identification of the neuropeptidases involved, and (iii) methods for the determination of neuropeptide stability in vitro. These methods are applicable also to study the degradation of peptide hormones by peripheral cells or tissues. To identify peptide degradation products, nanomolar amounts (micromolar concentrations) of peptides are incubated in synthetic media with cell or tissue cultures. Aliquots of the supernatants are withdrawn after different times, peptide fragments separated and fractionated by reversed-phase HPLC, and identified by peptide chemical methods. The peptidases responsible for this degradation can be identified by the use of specific inhibitors listed in the protocol. For receptor binding assays or the study of peptide effects in physiological, nanomolar concentrations the stability of the peptides in an in vitro system should be checked by addition of radiolabeled peptides (femtomolar or nanomolar concentrations) and monitoring the peptide degradation by a procedure analogous to that established for unlabeled peptides. The addition of more or less specific peptidase inhibitors enhances peptide stability in vitro, and thus it can be assured that a given peptide concentration is maintained during biological assays.     

Widespread expression of ecto-apyrase (CD39) in the central nervous system

We have shown that ecto-apyrase protein is expressed in primary neurons and astrocytes in cell culture (T.-F. Wang, P.A. Rosenberg, G. Guidotti, 1997. Mol. Brain Res. 1997, 47: 295-302). Here we present immunohistochemical studies showing that ecto-apyrase protein is widely distributed in rat brain, as it is present in neurons of the cerebral cortex, hippocampus and cerebellum as well as in glial cells and endothelial cells. Ecto-apyrase is enriched in brain postsynaptic density membrane fractions and is localized in proximity to synaptophysin, the marker of synaptic vesicles. These results together with the observation that P2 purinergic receptors are present throughout the brain suggest that ecto-apyrase is involved in regulating synaptic transmission mediated by extracellular ATP.