Titan's magnetic field signature during the first Cassini encounter

The magnetic field signature obtained by Cassini during its first close encounter with Titan on 26 October 2004 is presented and explained in terms of an advanced model. Titan was inside the saturnian magnetosphere. A magnetic field minimum before closest approach marked Cassini's entry into the magnetic ionopause layer. Cassini then left the northern and entered the southern magnetic tail lobe. The magnetic field before and after the encounter was approximately constant for approximately 20 Titan radii, but the field orientation changed exactly at the location of Titan's orbit. No evidence of an internal magnetic field at Titan was detected.     

Nitrate contents of kohlrabi (Brassica oleracea L. var. Gongylodes Lam.) as influenced by fertilization

The influence of different nitrogen doses given in different nitrogen forms on the nitrate contents of kohlrabi plants was examined in greenhouse-and field experiments. Increasing nitrogen amounts applied are followed by an increase in the nitrate contents of kohirabi. Nitrate fertilizers resulted in the highest and calcium cyanamide in the lowest nitrate contents. The nitrate contents of kohlrabi tubers sharply decreased along with prolonged period of time between the last nitrogen fertilization and harvesting. The nitrate increase was highest in the leaf stalks on the external and middle leaves but was only 20 to 25% of that level in the leaf blades and in tubers. At about the same level of nitrogen fertilization, nitrate contents of greenhouse kohlrabi cultivated at a time of year poor in light were considerably higher than those of fieldgrown kohlrabi in summertime.     

Daily blood feeding rhythms of laboratory-reared North American Culex pipiens

Background

Blood feeding by free-living insect vectors of disease is rhythmic and can be used to predict when infectious bites will occur. These daily rhythms can also be targeted by control measures, as in insecticide-treated nets. Culex pipiens form pipiens and C.p. f. molestus are two members of the Culex pipiens assemblage and vectors of West Nile Virus throughout North America. Although Culex species vector human pathogens and parasites, the daily blood feeding rhythms of C.p. f. molestus, to our knowledge, have not been studied. We described and compared the daily blood feeding rhythms of three laboratory-reared populations of Culex pipiens, one of which has confirmed molestus ancestry. We also examined the plasticity of blood feeding time for these three populations.

Results

For most (>70%) C.p. f. pipiens and C.p. f. molestus collected from metropolitan Chicago, IL, blood feeding took place during scotophase. Peak blood feeding occurred in mid-scotophase, 3-6 hours after lights off. For C.p. f. pipiens originating from Pennsylvania, most mosquitoes (> 90%) blood fed during late photophase and early scotophase. C.p. f. molestus denied a blood meal during scotophase were less likely to blood feed during early photophase (< 20%) than were C.p. f. pipiens from Chicago (> 50%). C.p. f. pipiens from Pennsylvania were capable of feeding readily at any hour of photo- or scotophase.

Conclusions

Daily blood feeding rhythms of C.p. f. molestus are similar to those of C.p. f. pipiens, particularly when populations originate from the same geographic region. However, the timing of blood feeding is more flexible for C.p. f. pipiens populations relative to C.p. f. molestus.     

Fresh and preserved green fodder modify effects of urinary acidifiers on urine pH of horses

Hay stabilises urine pH in horses. It is unknown whether this is an effect of structure or of chemical composition. In this study, four ponies (230–384 kg body weight [BW]) were fed six different diets with either a structure or a composition similar to hay with and without acidifiers in a cross‐over experimental design in amounts to maintain body weight with the following main compounds: Fresh grass (GRASS), alfalfa hay (ALF), grass cobs (COBS), grass silage (SIL), straw (STR) or extruded straw (STRe) for 2 to 10 days. Urine pH was measured in all trials, blood pH, blood base excess and bicarbonate as well as mineral balance were determined in GRASS, ALF, STR and STRe. In the trials with straw and extruded straw, urine pH decreased significantly (STR control: 7.8 ± 0.23, acidifier: 5.2 ± 0.38) when acidifiers were added, whereas in all other diets that were based on fresh or preserved green fodder, pH did not decrease below 7. Blood pH was similarly affected by diet and acidifiers. Acidifiers had little effect on the pre‐prandial blood pH, only in diet STR there was a significant reduction in relation to control. Post‐prandial blood pH was significantly reduced by acidifiers in all diets. Blood bicarbonate and base excess showed corresponding effects. Faecal and renal mineral excretion and apparent mineral digestibility were not systematically affected by diet or acidifiers except for chloride. Chloride added as inorganic chloride salt had an even better apparent digestibility than chloride originating from feed. Because only green plant material stabilised acid base balance, chlorophyll and its metabolites are discussed as potential mediators of the effect of green fodder on acid base balance.     

Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability

Preserving multicentennial climate variability in long tree-ring records is critically important for reconstructing the full range of temperature variability over the past 1000 years. This allows the putative "Medieval Warm Period" (MWP) to be described and to be compared with 20th-century warming in modeling and attribution studies. We demonstrate that carefully selected tree-ring chronologies from 14 sites in the Northern Hemisphere (NH) extratropics can preserve such coherent large-scale, multicentennial temperature trends if proper methods of analysis are used. In addition, we show that the average of these chronologies supports the large-scale occurrence of the MWP over the NH extratropics.     

Estimation of genetic parameters and genome scan for 15 semen characteristics traits of Holstein bulls

A QTL detection experiment was performed in French dairy cattle to search for QTL related to male fertility. Ten families, involving a total of 515 bulls, were phenotyped for ejaculated volume and sperm concentration, number of spermatozoa, motility, velocity, percentage of motile spermatozoa after thawing and abnormal spermatozoa. A set of 148 microsatellite markers were used to realize a genome scan. First, genetic parameters were estimated for all traits. Semen production traits were found to have moderate heritabilities (from 0.15 to 0.30) while some of the semen quality traits such as motility had high heritabilities (close to 0.60). Genetic correlations among traits showed negative relationships between volume and concentration and between volume and most quality traits such as motility or abnormal sperm while correlations between concentration and these traits were rather favourable. Percentages of abnormal sperm were negatively related to quality traits, especially with motility and velocity of spermatozoa. Three QTL related to abnormal sperm frequencies were significant at p < 0.01. In total, 11 QTL (p < 0.05) were detected. However, the number of QTL detected was within the range of expected false positives. Because of the lack of power to find QTL in this design further analyses are required to confirm these QTL.     

Rot holes create key microhabitats for epiphytic lichens and bryophytes on beech (Fagus sylvatica)

Identification of trees with key microhabitats as well as knowledge of their ecological formation is important for the conservation of epiphytic bryophytes and lichens on beech. Based on the hypothesis that certain types of stem damage are crucial for the occurrence of epiphytes of conservation concern, we surveyed 145 beech trees (57-280 years) for different types of stem damage and analysed their relationship to other tree characteristics, epiphyte species and wood-inhabiting fungi in a forest landscape on acid soils.Three main types of stem damage were identified; canker, rot hole and surface rot. The incidence of rot holes was highest on trees with a low growth rate during the last 50 years, but was unrelated to tree size or age per se. Bark pH was significantly higher below than above rot holes, whereas no such relationship was found for cankers. Wood mould from rot holes had a very high pH, explaining the higher bark pH below this type of damage. The number of epiphyte species of conservation concern was strongly positively related to rot holes and high bark pH. Cankers had a weaker, yet significant positive effect. The fungus Psathyrella cernua was associated with the rot holes and is suggested to be a key species involved in creating this microhabitat.We conclude that slow-growing trees with rot holes are important for the conservation of epiphytes and should be selected as retention trees in managed forests. The study also highlights a potential for habitat restoration by inducing artificial damage and inoculation of decay fungi in beech trees.