New data on sulphur valence and magmatic oxidation state for Central Andean volcanic rocks, in combination with published data for experimental and natural samples, allow derivation of a simple relationship between magma oxidation state and sulphur speciation. For a number of highly oxidized Central Andean volcanic rocks f O2 has been calculated using magnetite-ilmenite or olivine-spinel pairs and the sulphur valence in glasses has been measured using the peak shift of S-Kα radiation relative to a pyrite standard. Previously published experimental and natural data have been incorporated with a wider range in f O2 and S valence. The variation in sulphur speciation (as S2- or SO4 2-) as a function of log f O2 is described by an empirical polynomial fit which reproduces the data to within ±0.5 log units and allows use of electron microprobe measurements of the S-Kα wavelength shift for estimation of magmatic oxygen fugacities. This approach is applicable for f O2 between FMQ-2 and FMQ+6, encompassing most terrestrial magmas. The method has been used to calculate the in f O2 conditions under which melt inclusions were trapped in andesitic magmas before magma mixing in two Central Andean volcanoes, and to calculate the oxygen fugacity of a slowly-cooled pyroclastic flow in which the Fe-Ti oxide phases have subsequently re-equilibrated. In combination with Fe-Ti oxide data, two distinct trends emerge for Lascar volcano. Basaltic andesite-andesitic magma chambers follow T-f O2 trends which parallel the FMQ buffer curve, indicating ferrous-ferric iron buffering of oxygen fugacity. Dacitic anhydrite-bearing magmas with admixed basaltic andesite and andesite follow trends of increasing f O2 with decreasing temperature, indicative of buffering of f O2 by SO2-H2S in a co-magmatic gas phase. This trend continues into the metamorphic aureole of the magma chamber, resulting in highly oxidized (close to magnetite-hematite) conditions.

A recent meta-analysis of antidepressant trials is the largest conducted to date. Although it claims to prove antidepressant effectiveness beyond dispute, the main outcome is response rates, which are derived from continuous data in a process that can inflate differences between groups. The standardised mean difference of 0.3 is in line with other meta-analyses that show small differences between antidepressants and placebo that are unlikely to be clinically significant. Other factors likely to exaggerate the effects are discussed, and evidence on associations between antidepressant effects and severity and outcomes of long-term treatment is considered. Clinicians need to have open discussions with patients about the limitations of antidepressant research, the lack of evidence that antidepressants correct a chemical imbalance or other brain abnormality, and the range of adverse effects and mental and physical alterations they can produce.

During 1988 and 1989, the mesenteric veins of 901 cattle were examined for the presence of schistosomes at the Kandy slaughterhouse (Sri Lanka). The overall prevalence of infection was 31·2%. Animals younger than 2 years were less infected (21·3%) than those older than 5 years (47·9%). Based on the number of paired worms counted, three intensities of infection were recognized: low (1–20 pairs), moderate (21–100 pairs) and heavy (> 100 pairs). Intensities increased with the age of the animals but remained low (average 10 worm pairs). The worm burden increased by approximately 20% for each step in age group. The number of miracidia/100 g faeces was measured in 85 animals of all age groups and intensities of infection; 77% of the samples contained less than 100 miracidia. Miracidia counts decreased with age; moderately and heavily infected animals in each age group had the highest and the lowest counts, respectively. This may be due to a host immune response. The results raise questions on the sensitivity of faecal egg counts as a diagnostic method for visceral schistosomiasis in cattle.

One manner in which elephants utilize trees is by removing their bark. This type of utilization is concentrated on the largest trees in the landscape. The role of bark removal in increasing the vulnerability of large trees to fire and the mechanism through which fire damage is mediated were investigated in Kruger National Park, South Africa, by experimentally removing bark and burning Acacia nigrescens stems with diameters ranging between 30 and 68 mm. Also, field surveys were conducted subsequent to natural fires in order to investigate mortality patterns of large trees with dbh greater than 15 cm with bark removed by elephants. An increasing probability of mortality was associated with increasing amounts of bark removal but only if trees were burned. When trees had bark removed but were not burnt, simulating damage only to cambium and phloem, none of the 12 treated stems died in the 4-mo period over which the experiment ran. Moreover, low levels of cambium damage were detected in large burned stems. This suggests that bark removal increases fire-induced xylem damage and that this damage contributes towards stem mortality. In a survey of 437 large trees, bark removal by elephants was frequent on large stems (44%) and larger trees have greater amounts of bark removed. Post-fire mortality of large trees was significantly associated with increasing bark removal and stem diameter. These results indicate that bark removal by elephants increases the vulnerability of stems to fire, resulting in mortality of large stems otherwise protected from fire.

The vectorial capacity of Biomphalaria pfeifferi from Ndiangue, Senegal, was investigated with an allopatric isolate of Schistosoma mansoni from Nkolbisson, Cameroon. The snail infection rate after exposure to a single miracidium per snail (MD1) was 56·3%, and 91·6% for snails exposed to 5 miracidia per snail (MD5). The minimum pre-patent period was 21 days. The mean total cercarial production for the MD1 group was 18511 cercariae per snail, and 9757 cercariae for the MD5 group. The maximum production of cercariae for 1 day was 4892 observed in a snail from the MD1 group at day 43 post-infection. The mean longevity of snails was higher in group MD1 (88 days p.i.) than in group MD5 (65 days p.i.). The chronobiological emergence pattern revealed a circadian rhythm with one shedding peak at mid-day. Comparisons are made with the vectorial capacity of the sympatric combination of B. pfeifferi Senegal/S. mansoni Senegal.

The experiment examined the effect of breed, diet and sex on pig performance and carcass quality. Eight sires of the Duroc and Large White breeds each produced four experimental litters. Two boar and two female pigs from each litter were reared under standard conditions to 38 kg and then one of each sex was allocated to each of two finishing diets. These were cereal-based diets with and without 16 g/kg soya oil. Following slaughter at 80 kg, loin chops taken from half of the pigs (two litters per sire) were subjected to detailed investigation of physical, chemical and organoleptic characteristics. Lifetime live-weight gain was similar for both breeds but Duroc-sired pigs had greater voluntary food intakes and poorer food conversion efficiencies in the finishing stage. They also had greater killing-out proportions (775 v. 755 g/kg, P < 0·001) and backfat thickness at slaughter (284 v. 27·2 mm at P1 + P3, P < 0·05). Fat firmness measured by penetrometer at 4°C was lower in Duroc-sired pigs (738 v. 792 units, P < 0·001). The proportion of extractable intramuscular lipid was greater in chops from Duroc-sired pigs (13·8 v. 10·4 g/kg, P < 0·001). There were no significant effects of breed or diet on the eating quality of the grilled chops as assessed by a trained taste panel and a consumer panel.

Increasing concern has been expressed about deterioration in the handling and eating quality of pigmeat produced in modern U.K. circumstances. Many of the problems are attributed to excessive leanness. It has been suggested that the Duroc breed may produce a better quality product than current U.K. white breeds as a result of its higher level of intramuscular fat. Diet composition has also changed over time, with increasing use of a wider variety of ingredients and added fats. This experiment was carried out to examine the effects of breed and dietary fat on pigmeat quality characteristics.