Solvent switching of intramolecular energy transfer in bichromophoric systems: photophysics of (2,2'-bipyridine)tetracyanoruthenate(II)/pyrenyl complexes

The supramolecular systems [Ru(Pyr(n)bpy)(CN)(4)](2-) (n = 1, 2), where one and two pyrenyl units are linked via two-methylene bridges to the [Ru(bpy)(CN)(4)](2-) chromophore, have been synthesized. The photophysical properties of these systems, which contain a highly solvatochromic metal complex moiety, have been investigated in water, methanol, and acetonitrile. In all solvents, prompt and efficient singlet-singlet energy transfer takes places from the pyrene to the inorganic moiety. Energy transfer at the triplet level, on the other hand, is dramatically solvent dependent. In water, the metal-to-ligand charge transfer (MLCT) emission of the Ru-based chromophore is completely quenched, and rapid (200 ps for n = 1) irreversible triplet energy transfer to the pyrene units is detected in ultrafast spectroscopy. In acetonitrile, the MLCT emission is practically unaffected by the presence of the pyrenyl chromophore, implying the absence of any intercomponent triplet energy transfer. In methanol, triplet energy transfer leads to an equilibrium between the excited chromophores, with considerable elongation of the MLCT lifetime. The investigation of the [Ru(Pyr(n)bpy)(CN)(4)](2-) systems in methanol provided a very detailed and self-consistent picture: (i) The initially formed MLCT state relaxes toward equilibrium in 0.5-1.3 ns (n = 1, 2), as monitored both by ultrafast transient absorption and by time-correlated single photon counting. (ii) The two excited chromophores decay with a common lifetime of 260-450 ns (n = 1, 2), as determined from the decay of MLCT emission (slow component) and of the pyrene triplet absorption. (iii) These equilibrium lifetimes are fully consistent with the excited-state partition of 12-6% MLCT (n = 1-2), independently measured from preexponential factors of the emission decay. Altogether, the results demonstrate how site-specific solvent effects can be used to control the direction of intercomponent energy flow in bichromophoric systems.

Ticks and tick-borne diseases as a constraint to sheep and goat production in Italy. Selected features

The paper reviews basic information on small ruminant production in Italy and on the tick species commonly found on them. A total of 13 Ixodidae species have been reported to parasitise sheep in the country. The tick species were belonging to five genera: Ixodes (two species), Haemaphysalis (four species), Dermacentor (one species), Rhipicephalus (three species) and Hyalomma (three species). The same species, with the exception of Haemaphysalis inermis and Hyalomma detritum have been reported also on goats. Scarse data are available on the impact of tick borne diseases on small ruminants productivity. The zoonotic role which may be played by ticks in transmitting occupationally acquired diseases to people involved in animal husbandry and to common public which may accidentally invade grazing areas is also discussed.

Sero-prevalences of selected cattle diseases in the Kafue flats of Zambia

Sera from five traditionally managed herds grazing in the Kafue flats were tested for antibodies to bovine viral diarrhoea-mucosal disease (BVD-MD), parainfluenza 3 (PI3), infectious bovine rhinotracheitis-infectious pustular vulvovaginitis (IBR-IPV), bovine adenovirus 3 (BAV3) and Bluetongue (BT). The sero-prevalences of the first four diseases were respectively 76.2, 94.4, 42.1 and 87.4%. Five samples (2.3%) gave doubtful reactions for BT. Prevalences of 28.5% for brucellosis, 14% for Rift Valley fever (RFV), 0.9% for Q fever and 11.2% for chlamydiosis were also recorded. Significantly higher values for BVD-MD (p less than 0.005), IBR-IPV (p less than 0.01) and brucellosis (p less than 0.05) were found in animals over 1 year of age. No differences were recorded between herds or between male and female animals. The high concentration of wild and domestic ruminants grazing together in the flood plains during the dry season may be a major determinant of the high values observed. Traditional farmers, slaughterhouse workers and other people involved in livestock production are particularly at risk of contracting brucellosis and RVF because of the high prevalences in cattle and local habits favourable to their transmission.

Amblyomma marmoreum on tortoises of southern province, Zambia

Reptiles from Southern Province, Zambia were captured and inspected for ticks. Seven of 18 tortoises (Geochelone pardalis) were infested by small numbers of adults and nymphs of Amblyomma marmoreum. Under such circumstances, the tick had little apparent effect on the host. None of the 13 specimens representing four species of snakes examined were infested with ticks.

Thelazia rhodesii (Desmarest, 1828) in cattle of Central Province, Zambia

Sanga cattle from Central Zambia were examined during the dry and the rainy seasons for the presence of the adult stage of eyeworm Thelazia rhodesii. Prevalences were recorded according to age/sex groups. The occurrence of ocular diseases was also noted. Differences between the total prevalences of infection with the parasite in the dry and rainy seasons were observed: respectively 3.1% and 26.6% of all cattle examined (p less than 0.001), which numbered 223 head in the dry season and 248 in the rainy season. In both seasons, adult males showed the highest prevalence and calves the lowest. In the dry season the parasite was found in two of the 23 males (8.7%) but in none of the 24 calves. During the rains, eight of the 22 adult males (36.4%), and two of 53 calves (3.8%) were parasitized (p less than 0.001). A comparison of the prevalences in the latter season between a group of cows sprayed weekly with a synthetic pyrethroid and an untreated group showed no significant difference between the two groups (p greater than 0.1). No correlation was found between T. rhodesii infection and the occurrence of eye lesions (p greater than 0.1). It is concluded that in traditionally managed Zambian cattle the infection is seasonal, is more frequent in adult male animals and is not associated with eye infections (i.e., pink-eye).