Thermal treatment of 2,4,6-trichlorophenol on a magnesium silicate-based model fly ash in the temperature range between 250 degrees C and 400 degrees C leads predominantly to carbon monoxide and carbon dioxide. The fraction of 2,4,6-trichlorophenol which is oxidized to CO and CO2 increases from 3% at 250 degrees C to 75% at 400 degrees C. Further products are polychlorinated benzenes, dibenzo-p-dioxins, dibenzofurans and phenols. The homologue and isomer patterns of the chlorobenzenes suggest chlorination in the ipso-position of the trichlorophenol. The formation of PCDD from 2,4,6-trichlorophenol and 2,3,4,6-tetrachlorophenol on municipal solid waste incinerator fly ashes and model fly ash were compared and the reaction order calculated.

Journal Article↗

PubMedDate not supplied

Mechanistic studies on the role of PAHs and related compounds in PCDD/F formation on model fly ashes.

Model fly ashes containing Florisil, CuCl2.2H2O and PAHs with structures similar to dibenzo-p-dioxin or dibenzofuran were heated at 250 degrees C in He/O2 with regard to a supposed intramolecular reaction mechanism for oxygen incorporation. Highest reactivities in PCDF formation could be found for model compounds containing a biphenyl structure, while condensed pi-systems lead to a decrease in reactivity for such compounds. Biphenyl is almost completely converted to dibenzofuran. PCDD formation from six-membered rings like xanthene/9,10-dihydroanthracene is of minor importance. 18O-labeling of gaseous oxygen reveals no common reaction step for oxygen incorporation using 9-fluorenone, xanthene, diphenyl ether and diphenyl-2-carboxylic acid as model compounds. Pre-existing oxygen in reactants is a major source for ether groups in PCDD and PCDF. Determination of labeled and unlabeled CO and CO2 besides He/O2 reflects higher reactivities towards oxidation for model compounds containing ether groups than for compounds with carbonyl groups.

Journal Article↗

PubMedDate not supplied

Osteoporosis in early ankylosing spondylitis: a primary pathological event?

Patients with severe ankylosing spondylitis of long duration often have spinal osteoporosis secondary to ankylosis and immobility. Bone mineral density of defined regions of the lumbar spine, femoral neck, and carpus was measured in 25 men who met accepted diagnostic criteria for ankylosing spondylitis but had early disease, with normal mobility and no, or very minor, radiological evidence of lumbar spine involvement. Compared with age-matched male controls, patients with ankylosing spondylitis had a significantly lower hydroxyapatite density in the lumbar spine (mean [SD] 0.82 g/cm2 [0.12] vs 0.91 g/cm2 [0.11]) and in the femoral neck (0.83 g/cm2 [0.11] vs 0.92 g/cm2 [0.11]). There was no significant difference in carpal bone mineralisation density. The pattern of bone loss in these patients indicates early loss of trabecular bone in ankylosing spondylitis, possibly from a systemic cause, but biochemical indices of calcium turnover were similar in patients and controls.

Adolescent↗

PubMedDate not supplied

[Experiences with the use of BAYVAROL STRIPS in beehives in warehouses and post-treatment hives for control of varroatosis under practice conditions].

BAYVAROL STRIPS are a highly efficient remedy against varroatosis. When applied according to the directions for use, the bee colonies can be protected from Varroa induced collapse in the late summer. Moreover BAYVAROL STRIPS help in the development of healthy winter bees and guarantee the hibernation of strong bee colonies. A change of nowadays control strategy is possible only when breeding of bees resistant to Varroa jacobsoni will succeed (Büchler, 1992).

Animals↗