Saturn's moon Enceladus has vents emerging from a sub-surface ocean, offering unique probes into the liquid environment. These vents drain into the larger neutral torus in orbit around Saturn. We present a methanol (CH3OH) detection observed with IRAM 30-m from 2008 along the line-of-sight through Saturn's E-ring. Additionally, we also present supporting observations from the Herschel public archive of water (ortho-H2O; 1669.9 GHz) from 2012 at a similar elongation and line-of-sight. The CH3OH 5(1,1)-4(1,1) transition was detected at 5.9σ confidence. The line has 0.43 km s−1 width and is offset by +8.1 km s−1 in the moon's reference frame. Radiative transfer models allow for gas cloud dimensions from 1750 km up to the telescope beam diameter ~73 000 km. Taking into account the CH3OH lifetime against solar photodissociation and the redshifted line velocity, there are two possible explanations for the CH3OH emission: methanol is primarily a secondary product of chemical interactions within the neutral torus that: (1) spreads outward throughout the E-ring or (2) originates from a compact, confined gas cloud lagging Enceladus by several km s−1. We find either scenario to be consistent with significant redshifted H2O emission (4σ) measured from the Herschel public archive. The measured CH3OH:H2O abundance (>0.5%) significantly exceeds the observed abundance in the direct vicinity of the vents (~0.01%), suggesting CH3OH is likely chemically processed within the gas cloud with methane (CH4) as its parent species.

In the Weichselian, the Lower Rhine in the Dutch-German border region has used three courses, dissecting ice-marginal topography inherited from the Saalian. In the Late Weichselian, the three courses functioned simultaneously, with the central one gaining importance and the outer ones abandoning. This study aims to reconstruct the fluvial development and forcings that culminated in abandonment of the northern branch ‘Oude IJssel-Rhine’, at the time of the Lateglacial to Holocene transition. The fluvial architecture is studied using a cored transect over the full width of the valley, detailed cross-sections over palaeochannels and geomorphological analysis using digital elevation and borehole data. Biostratigraphy, radiocarbon dating and OSL dating provide a timeframe to reconstruct the temporal fluvial development. In its phase of abandonment, the fluvial evolution of the Oude IJssel-Rhine course is controlled by the ameliorating climate and related vegetation and discharge changes, besides by intrinsic (autogenic) fluvial behaviour such as the competition for discharge with the winning central branch and the vicinity of the Lippe tributary confluence. The rapid climate warming at the start of the Late Glacial resulted in flow contraction as the initial response. Other fluvial geomorphic adjustments followed, with some delay. An aggrading braided or transitional system persisted until the start of the Allerød, when channel patterns finally changed to meandering. Floodplain incision occurred at the Allerød - Younger Dryas transition and a multi-channel system developed fed by Rhine discharge. At the start of the Holocene, this system transformed into a small-scale, local meandering system, which was abandoned shortly after the start of the Holocene.

The final abandonment of the Oude IJssel-Rhine and Niers-Rhine courses can be attributed to deep incision of the Central Rhine course in the earliest Holocene and is considered to be controlled by flow contraction induced by climate and related vegetation and discharge changes.

Risky decision making, a hallmark phenotype of substance use disorders (SUD), is thought to be associated with deficient feedback processing. Whether these aberrations are present prior to SUD onset or reflect merely a consequence of chronic substance use on the brain remains unclear. The present study investigated whether blunted feedback processing during risky decision making reflects a biological predisposition to SUD. We assessed event-related potentials elicited by positive and negative feedback during performance of a modified version of the Balloon Analogue Risk Task (BART) among high-risk adolescents with a parental history of SUD (HR; n = 61) and normal-risk controls (NR; n = 91). HR males made significantly more risky and faster decisions during the BART than did NR controls. Moreover, HR adolescents showed significantly reduced P300 amplitudes in response to both positive and negative feedback as compared to NR controls. These differences were not secondary to prolonged substance use exposure. Results are discussed in terms of feedback-specific processes. Reduced P300 amplitudes in the BART may reflect poor processing of feedback at the level of overall salience, which may keep people from effectively predicting the probability of future gains and losses. Though conclusions are tentative, blunted feedback processing during risky decision making may represent a promising endophenotypic vulnerability marker for SUD.

For over a decade, the structure of the inner “hole” in the transition disk around TW Hydrae has been a subject of debate. To probe the innermost regions of the protoplanetary disk, observations at the highest possible spatial resolution are required. We present new interferometric data of TW Hya from near-infrared to millimeter wavelengths. We confront existing models of the disk structure with the complete data set and develop a new, detailed radiative-transfer model. This model is characterized by: 1) a spatial separation of the largest grains from the small disk grains; and 2) a smooth inner rim structure, rather than a sharp disk edge.

Using photometry at just two wavelengths it is possible to fit a blackbody to the spectrum of infrared excess that is the signature of a debris disc. From this the location of the dust can be inferred. However, it is well known that dust in debris discs is not a perfect blackbody. By resolving debris discs we can find the actual location of the dust and compare this to that inferred from the blackbody fit. Using the Herschel Space Observatory we resolved many systems as part of the DEBRIS survey. Here we discuss a sample of 9 discs surrounding A stars and find that the discs are actually located between 1 and 2.5 times further from their star than predicted by blackbody fits to the spectral energy distribution (SED). The variation in this ratio is due to differences in stellar luminosities, location of the dust, size distribution and composition of the dust.

Trials of rodenticidal baits containing 50 p.p.m. difenacoum, 50 p.p.m. bromadiolone or 20 p.p.m. brodifacoum were carried out on farmsteads against populations of Rattus norvegicus containing difenacoum-resistant individuals. Six difenacoum treatments failed in 14–42 days of baiting. Two treatments with bromadiolone succeeded in 23 and 33 days, but four further treatments lasting 35–56 days failed to eradicate the populations. Brodifacoum gave virtually complete control of six populations in 21–73 days and of the ten residual populations left behind by the other two compounds, after baiting for a further 11–85 days. The performance of both bromadiolone and brodifacoum was well below that reported by previous investigators, indicating the possibility of low-grade resistance to these compounds in the difenacoum-resistant strain.

The potentiality of calciferol (alone and combined with warfarin) for the control of commensal rats and mice has been examined in the laboratory. Nearly all animals fed on 0·1% calciferol for 2 days died. Though illness usually reduced food intake after the first 24 hr. there was no sign of aversion to the poison at 0·1 % – which is considered to be the lowest concentration suitable for use against Rattus norvegicus, R. rattus and Mus musculus in the field. There was some indication that resistance to warfarin in R. norvegicus may be correlated with susceptibility to calciferol. Toxicity tests with calciferol combined with warfarin indicated an additive effect between the compounds. No evidence for synergism was found however, although elsewhere there is some evidence for this.

Three South-Asian rodent pest species were tested for susceptibility to anticoagulant rodenticides. Wheat flour containing 0·025% warfarin, 0·0375% coumatetralyl or 0·005% difenacoum was fed to 260 Tatera indica, 140 Nesokia indica and 81 Bandicota bengalensis for 1–56 days. Tatera was about as susceptible to anticoagulants as Rattus rattus has been reported to be. Nesokia and Bandicota were extremely variable: though the majority were highly susceptible, the slopes of the dose-mortality curves were close to zero. The difenacoum diet appeared to be more toxic than the warfarin diet to all three species, but less toxic than the coumatetralyl diet to Tatera and Nesokia. All of the anticoagulants were eventually lethal to all of the animals tested.

Laboratory tests were carried out to assess the efficacy of gophacide as a rodenticide against the Norway rat (Rattus norvegicus) and the house mouse (Mus musculus). Results of feeding tests with wild animals suggest that the compound would be more useful against mice than rats, and that 0.3% would be a near optimal concentration for field trials for both species.

The hazards of using gophacide as a rodenticide are discussed.

The toxicity and palatability of coumatetralyl (3-(α-tetralyl)-4-hydroxycoumarin) to rats (Rattus norvegicus Berk.) were investigated in the laboratory by means of feeding tests. Animals resistant to warfarin (3-(α-acetonylbenzyl)-4-hydroxy-coumarin) and warfarin-resistant rats from infestations refractory to coumatetralyl, as well as non-resistant animals, were employed in the tests.

Medium oatmeal containing a concentration of 0·1% coumatetralyl was not markedly less palatable than the same food unpoisoned. In comparison warfarin at 0·05% but not at 0·025% was significantly less readily eaten than the plain food. Coumatetralyl at 0·05% and 0·005% was about as toxic as 0·005% warfarin is reported to be to non-resistant rats. Warfarin-resistant rats were significantly less susceptible to coumatetralyl than were non-resistant rats. Warfarin-resistant rats from an infestation refractory to coumatetralyl were significantly less susceptible to coumatetralyl than were animals from other sources.

It is considered that coumatetralyl at concentrations of the order of 0·05% in bait would be a good alternative to warfarin against non-resistant rats. While it would be expected that, at this concentration, coumatetralyl would often give good results against warfarin-resistant infestations, this use might eventually produce an increase in the incidence of resistance to both anticoagulants.

We thank Baywood Chemicals Ltd., for supplying the coumatetralyl used in this work. We are also indebted to several colleagues for supplying wild rats and information on field investigations and to Messrs G. Snell and P. Romer for technical assistance.

1. Field trials suggest that 3-monthly operations against rats in sewers using either 0·25% sodium fluoracetate or 2% fluoracetamide as a direct poison are more effective than 6-monthly treatments with 2·5% zinc phosphide or 10% arsenious oxide using the pre-baiting method.

2. In six paired trials 2% fluoracetamide gave better results (an apparent 100% clearance in five instances) than 0·25% sodium fluoracetate.

3. There is no evidence, at present, that direct poisoning treatments with 2% fluoracetamide or 0·25% sodium fluoracetate are improved by the addition of mould inhibiting substances to the bait.

The work described above was made possible only by the co-operation of a large number of local authority councils and their staffs, to whom we are therefore much indebted. We wish to thank also, Mr J. D. Riley who gave considerable help during the early stages of the trials.

The properties of 5-p-chlorophenyl silatrane as a rodenticide against Rattus norvegicus and Mus musculus were investigated in the laboratory. The high oral toxicity of the compound was confirmed. When the compound was given to laboratory rats and mice by stomach tube at lethal dosages, signs of poisoning were observed within a minute. When caged wild rats and mice were given a choice between plain and poisoned baits the optimum rodenticidal concentration in the bait was about 0.5% for both species, producing 50% mortality in wild rats and 95% mortality in wild mice. The results are discussed in relation to safety in use and the probable effectiveness of the compound as a rodenticide in field conditions.

1. The average lethal dose of fluoracetamide for wild R. norvegicus was found to be 13 mg./kg. of body weight and the LD95, about 43 mg./kg.

2. Wild rats offered bait contatining 0·5, 1 and 2% fluoracetamide, after a period of conditioning, seemed to find it palatable and, on the average, ingested the equivalent of 18–100 LD50's. Warning symptoms appeared in about an hour or longer and included short convulsive spasms.

3. The speed of onset of warning symptoms leading to cessation of feeding was studied in albino rats dosed with the equivalent of 2 LD50's of sodium fluoracetate, zinc phosphide or fluoracetamide. Feeding ceased soonest in the case of sodium fluroacetate. Zinc phosphide gave very variable results, but it is thought that if wild rats had been used, feeding would have stopped nearly as soon as with sodium fluoracetate.

4. It is considered that field trials to compare the efficiency of 1% flouracetamide and 2·5% zinc phosphide, both with ‘prebaiting’, would be well justified.

5. Fluoracetamide at 2% may also prove to be a good alternative to 0·25% sodium fluoracetate as a ‘direct’ poison for controlling rats in sewers.

We are indebted to Miss Y. Larthe and Miss E. J. Taylor who took part in the bioassay and in one of the experiments with the marked rats.

The median lethal dose of orally administered norbormide for wild Rattus norvegicus found to be 9·0 mg./kg. of body weight and the LD 95 about 17·0 mg./kg.

In tests in which various concentrations of norbormide or zine phosphide were added to the food of individually caged wild rats, mortality increased with concentration of poison, though more slowly with norbormide than with zine phosphide. The mortality that occurred among rats offered a choice between unpoisoned food and the same food with added norbormide or zinc phosphide indicates that in control treatments in the field the optimum concentration of norbormide in bait would be about 0·;5% and that this might be expected to give results comparable with those obtainable with 2·;5% or 5·0% zine phosphide. Other methods of estimating suitable field strengths indicate that concentrations of norbormide higher than 0·;5% may be preferable.

Some animals that survived exposure to a choice of plain food and the same Food poisoned with norbormide or zine phosphide at field concentrations avoided mating lethal amounts by reacting to the taste of the poison. Others learned to use the taste of the food, not that of the poison as a cue and later avoided eating the food when it contained no poison.

When either poison was presented to rats in the more palatable of two foods in the choice situation mortality was relatively high. Some of the surviving animals subsequently rejected the more palatable food in preference to the normally less palatable alternative.

Wild populations of the Norway rat, Rattus norvegicus, in Jutland have been known to be resistant to the anticoagulant rodenticide warfarin since 1962. The inheritance of the resistance was investigated in the F1, backcross and intercross. The results are consistent with the resistance being due to a major gene at the Rw locus. Resistant homozygotes, heterozygotes and susceptible homozygotes appeared to be distinguishable experimentally on the basis of differences in their susceptibility to vitamin K deficiency. The results are discussed in relation to previous studies of the inheritance of warfarin resistance in rats.

The inheritance of resistance to the rodenticide, warfarin, in the Norway rat, Rattus norvegicus, derived from a wild rat population in Scotland was studied in the backcross, intercross and testcross. The resistance was found to be due to a major gene with about the same map position in Linkage Group I as the warfarin-resistance gene, Rw2, which occurs in the wild rat population in Wales. In heterozygotes, the Scottish resistance gene, unlike the Welsh gene, is incompletely penetrant in expression, though the penetrance was found to increase markedly in response to selection. Differences between the Scottish and Welsh types of resistance suggest that the two resistance genes are allelic.

The frequency of monogenic resistance to anticoagulant rodenticides in Rattus norvegicus in an area straddling the England–Wales border was monitored from 1967 until 1975. Rats were trapped on farms and tested in the laboratory by administering a dose of warfarin lethal to susceptibles. The mean incidence of resistance was 44% and did not change significantly, despite the extensive use of anticoagulants by farmers during the 9-year period. In 1975 more refined techniques showed that the frequencies of susceptible (SS) and resistant (RR) homozygotes were significantly below the Hardy–Weinberg expectations and simple estimates of the relative fitness ratios for the RR, RS and SS phenotypes were 0·37, 1·0 and 0·68 respectively. In two relatively isolated valleys, where selection with anticoagulants was minimal, the frequency of resistance decreased significantly from 57% to 39% during 1973–5. The results are consistent with the hypothesis that a balanced polymorphism is being maintained. Selection against susceptible homozygotes by the use of anticoagulant rodenticides, and against the resistant homozygote due to its high susceptibility to a primary deficiency of vitamin K gives the heterozygotes a selective advantage. A number of ecological factors that influence the incidence of the resistance are discussed briefly.

Two warfarin-resistant strains of the Norway rat, Rattus norvegicus, derived independently from wild populations in Wales and Scotland and both homozygous for a major gene at the warfarin-resistance locus, Rw, were found to differ in their hypoprothrombinaemic response to simultaneous dosage with warfarin and vitamin K. The Welsh strain gave a small response and the Scottish strain a large response. These two response levels segregated in Mendelian fashion in various crosses involving the two resistant strains and a third, non-resistant strain. This indicates that the Rw locus has a series of three multiple alleles, denoted Rww, Rws and Rw+. The results are discussed briefly in relation to biochemical, ecological and evolutionary aspects of warfarin resistance.