Application of alumina supported gold-based catalysts in total oxidation of CO and light hydrocarbons mixture

Gold nanoparticles supported on alumina have been produced using the anionic exchange method and ammonia washing procedure. The catalysts are tested in the reaction of total oxidation of a mixture of light hydrocarbons and carbon monoxide in order to study the possibility of application in the reduction of cold start emissions. The obtained results are promising according to the temperature range observed for the oxidation of unsaturated hydrocarbons. The results obtained for acetylene confirms the difference of oxidation of this hydrocarbon over gold catalysts. An ageing procedure has been employed. This procedure does not affect the comportment of the catalysts versus hydrocarbon oxidation.     

Etude du taux de recouvrement d'une electrode de nickel au cours du degagement d'oxygene

Oxygen discharge on a nickel electrode in the transpassive region is studied. In the potentiokinetic regime, the Tafel slopes depend on the polarisation parameters. A reaction mechanism taking account of the degree of coverage of the electrode with the species Ni---OH_ads is proposed, and an attempt is made to determine the coverage by studies of the influence of pH and that of temperature.

Zusammenfassung

Die Sauerstoffentaldung an einer Nickelektrode im transpassiven Gebiet wird untersucht. Im potentiokinetischen Gebiet hängen die Tafel-Steigungen von den Polarisationsparametern ab. Ein Reaktionsmechanismus, der den Bedeckungsgrad der Elektrode durch das Teilchen Ni---OH_ads berücksichtigt, wird vorgeschlagen; und es wird versucht, durch Untersuchung des Einflusses des pH und der Temperatur den Bedeckungsgrad zu bestimmen.     

Skin-lightening products revisited

Skin colour typology depends on the amount and location of its chromophores. Among them, eumelanins derived from 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI), and phaeomelanins are of utmost importance. These biomolecules result from the multi-step enzymatic and non-enzymatic conversion of tyrosine into melanins. Pigmentation disorders are multiple and depend on alterations in the density in active melanocytes, and on specific abnormalities of any of the complex melanogenesis mechanisms. This review presents some of the main skin-lightening agents with respect to their mechanisms of action and side-effects. Some of the novel compounds may lead to new perspectives in the fields of dermatology and cosmetology. The methods commonly used to assess efficacy of skin-lightening products rely on in vitro models including cell-free enzymatic assays, melanocyte cultures and reconstructed epidermis bioassays. Animal models have little relevance. By contrast, human testing with the support of instrumental evaluations is the most informative.     

Complementary techniques for unbiased stereology of brain ultrastructure

Estimating synaptic density is central to any examination of synaptic change. Barring techniques involving exhaustive sectioning, the traditional method for this estimation is the double dissector technique, which derives a ratio of synapses per neuron. This ratio, however, may not always equate to an absolute number of synapses. In contrast, the unbiased brick, while free of these problems, is limited by changes in reference space and cannot provide information on synaptic connectivity. Thus, the ideal analysis is to derive both synaptic measures. When these measures agree, one can discount changes in extraneous factors influencing synaptic counts.     

The Stimulation Program Health Research. X. Evaluation of the program section 'Psychogeriatrics'

In the programme section 'Psychogeriatrics' of the SGO Health Research Promotion Programme a longitudinal study was carried out in Amsterdam from 1989 until 1994, concerning the course of mild cognitive decline in elderly people (the AMSTEL project). The scientific aims were the development of diagnostical instruments for the early diagnosis of dementia, the development of criteria which predict the course of mild cognitive impairment and the expansion of knowledge on the relationship between somatic and psychiatric pathology and dementia. The programme also had aims regarding medical education and patient care. The results include the following: in order to diagnose dementia in general practice questions regarding orientation and short-term memory are helpful. Risk factors for cognitive deterioration in elderly people include hippocampal atrophy on the MRI scan, a low level of education and subjective complaints regarding memory. Subjective complaints regarding memory are not primarily caused by a depressive mood, as is often thought, but are important as correct self-observations of cognitive deterioration, and go with an increased risk of developing dementia. Besides the AMSTEL project a feasibility study was carried out concerning a psychogeriatric case register in Amsterdam.     

Immune response to the filaria Litomosoides sigmodontis in susceptible and resistant mice

Comparisons were made between the immune responses evoked during the course of chronic and patient infections of Litomosoides sigmodontis in susceptible BALB/c mice and non-patent infections in resistant B10.D2 mice. Early antigen specific responses of spleen cells were weak in both mouse strains. However, by day 58 post infection a strong Th2 response, as determined by production of IL-4, IL-5 and IL-10, was observed in BALB/c mice but not in B10.D2 mice. Antibody responses seemed to appear sooner in B10.D2 than in BALB/c mice, and these differentially recognised two antigens of 15 kD and 80 kD.     

Stimulation of thymocyte mitogenic protein secretion and of cytostatic activity of mouse peritoneal macrophages by trehalose dimycolate and muramyldipeptide

Immunomodulators of bacterial origin, such as muramyl-dipeptide (MDP) and trehalose dimycolate, are able to stimulate some important biological functions of macrophages, such as their capacity to secrete a monokine, the thymocyte mitogenic protein (TMP), and to limit the growth of mastocytoma cells in vitro. Adherent cells from the peritoneal cavity of untreated mice do not secrete significant amounts of TMP and are not cytostatic. In contrast, adherent peritoneal cells from mice injected with trehalose dimycolate (emulsified in water) secrete TMP and are strongly cytostatic for P815 cells. Trehalose dimycolate is also active when added in vitro: (a) it enhances the cytostatic action of thioglycollate-elicited macrophages; (b) alone or in sequence with MDP, it induces an appreciable cytostatic activity in resident macrophages; (c) it limits the decline of the strong cytostatic action of trehalose-dimycolate-elicited macrophages occurring during in vitro cultivation. MDP also stimulates the cytostatic activity of the macrophages in vitro. The most interesting effect of MDP is its capacity to induce a strong secretion of TMP after a short contact (1 h) with elicited macrophages.