Xenon Tetrafluoride: Heat of Formation

Calorimetric measurements of the heat of reaction of xenon tetrafluoride with aqueous iodide solution give -60 kilocalories per mole for the standard heat of formation, or an average thermochemical bond energy of about 31 kilocalories.     

Using GIS to measure changes in the temporal and spatial dynamics of forestland: experiences from north-west Spain

Forestry variables are usually calculated at a forest managementunit scale. However, a region's forestry sector is affectedby various other factors that interact over space and time,many of which are not directly associated to silvicultural activitiesbut nonetheless play an important part in its development froma socio-economic or environmental point of view. To understanda region's forestry dynamics, and especially to predict itsfuture tendencies, we must include all the necessary variablesin a single database, calculated for spatial units that arestable over time and adequate for planning purposes. In ourstudy, we developed a Forest Geographic Information System forGalicia called ‘SIFGa’. We used it to examine 310variables describing the environment, population tendencies,land tenure and forest management in the Spanish autonomousregion of Galicia, at both council and parish levels. Resultsreveal the connections between our variables, which reflectthe changes the regional forestry sector has experienced inthe past, and explain its current situation. They also confirmthe heterogeneity of forestry in the area and the need to adaptforest-planning strategies to each study unit, as well as tothe entire region.     

An investigation of factors associated with the prevalence of verocytotoxin producing Escherichia coli O157 shedding in Scottish beef cattle

The prevalence of verocytotoxin-producing Escherichia coli (VTEC) O157 in 12-30-month-old beef finishing cattle in Scotland was determined using 1g faeces samples enriched in buffered peptone water, followed by immunomagnetic separation (IMS) and isolation on sorbitol MacConkey agar with cefixime and tellurite supplement (CT-SMAC). A validated questionnaire was used to collect information that could be associated with the samples. Generalised Linear Models and Generalised Linear Mixed Models were used to identify factors associated with shedding both between and within groups. A total of 14,856 samples were collected from 952 farms, of which 1231 were positive for VTEC O157. Prevalence levels were calculated with 95% confidence intervals as follows: 7.9% (6.5%, 9.6%) of animals sampled were estimated to be shedding VTEC O157, while 22.8% (19.6%, 26.3%) of farms were estimated as having at least one animal shedding in the group sampled. The median percentage of animals shedding in positive groups was 25% (20%, 32%). An increased probability of a group containing a shedding animal was associated with larger numbers of finishing cattle, the presence of pigs on the farm, or the farm being classed as a dairy unit stocking beef animals. Farms that spread slurry on grazing land were more likely to have shedding animals, while those that spread manure were at lower risk. Groups with older animals were less likely to be identified as positive. There was no significant regional difference in group shedding probabilities, but the proportion of positive groups dropped over two successive years of the study. Higher mean levels of shedding in positive groups were associated with animals being housed rather than at pasture, and this effect was stronger in groups which had recently had a change in housing or diet. Farms with animals at pasture had lower mean prevalence where water was supplied from a natural source, as had farms with higher numbers of finishing cattle. There remained unexplained variability in mean prevalence levels on positive farms in different areas of Scotland.     

RNA‐based biocontrol compounds: current status and perspectives to reach the market

Facing current climate challenges and drastically reduced chemical options for plant protection, the exploitation of RNA interference (RNAi) as an agricultural biotechnology tool has unveiled possible new solutions to the global problems of agricultural losses caused by pests and other biotic and abiotic stresses. While the use of RNAi as a tool in agriculture is still limited to a few transgenic crops, and only adopted in restricted parts of the world, scientists and industry are already seeking innovations in leveraging and exploiting the potential of RNAi in the form of RNA‐based biocontrol compounds for external applications. Here, we highlight the expanding research and development pipeline, commercial landscape and regulatory environment surrounding the pursuit of RNA‐based biocontrol compounds with improved environmental profiles. The commitments of well‐established agrochemical companies to invest in research endeavours and the role of start‐up companies are crucial for the successful development of practical applications for these compounds. Additionally, the availability of standardized guidelines to tackle regulatory ambiguities surrounding RNA‐based biocontrol compounds will help to facilitate the entire commercialization process. Finally, communication to create awareness and public acceptance will be key to the deployment of these compounds. © 2019 Society of Chemical Industry     

Response of benthic cave invertebrates to organic pollution events

• 1. Even though the fragility and vulnerability of subterranean ecosystems (caves, groundwater and hyporheic habitats) is widely acknowledged, the impacts of human disturbances have been poorly quantified when compared with surface waters. In particular, limited data exist regarding the impact of organic pollution upon aquatic cave invertebrate communities.
• 2. The Peak–Speedwell Cavern system (Derbyshire, UK) was affected by two organic pollution events, during a 7‐year study (1997–2003), originating from the same source in the surface catchment but resulting in markedly different ecological responses. The first event led to the elimination of most taxa from affected sites while the second resulted in an increase in abundance of organisms within the cave associated with the increased availability of trophic resources. The second event also coincided with the invasion of the stygophilic amphipod, Gammarus pulex, at a site where it had not previously been recorded.
• 3. Recovery of the invertebrate community following both organic pollution events occurred within 12 months. Recolonization of the affected sites was facilitated by annual flooding of the cave and by the presence of refugia on unaffected subterranean tributaries.
• 4. The data highlight the problems associated with the conservation and management of subterranean ecosystems where impacts in distant surface catchments may have unseen repercussions for the subterranean environment. Aquatic subterranean habitats are not widely monitored and the impacts of pollution/disturbance may not be detected in surface waters for some time, if at all, owing to dilution effects. Caves supporting obligate subterranean organisms (stygobites) are particularly vulnerable to these pressures and require clear management strategies to protect both the subterranean and surface catchments which support them.

Copyright © 2008 John Wiley & Sons, Ltd.     

Bemerkung zum Aufsatz von H. Maercks: „Wird der Wasserhaushalt der Insekten durch das Daltonsche Gesetz bestimmt?”

Ohne Zusammenfassung Mit 1 Abbildung. Anzeiger für Sch?dlingskunde, Bd. 9, Heft 5, 1933.     

Geometrical aspects of sorted patterned ground in recurrently frozen soil

A model for sorted patterned ground shows that some types arise from density-driven Rayleigh free convection that occurs during thawing of water-saturated recurrently frozen soils. The regularly spaced convection cells result in an uneven melting of the underlying ice front. Frost action causes stones to be upthrusted and to form in a pattern on the ground surface that mirrors the corrugation in the underlying ice front. The implications of the water circulation direction in the cells on the sorting process are considered.     

Spongiform degeneration in mahoganoid mutant mice

mahoganoid is a mouse coat-color mutation whose pigmentary phenotype and genetic interactions resemble those of Attractin (Atrn). Atrn mutations also cause spongiform neurodegeneration. Here, we show that a null mutation for mahoganoid causes a similar age-dependent neuropathology that includes many features of prion diseases but without accumulation of protease-resistant prion protein. The gene mutated in mahoganoid encodes a RING-containing protein with E3 ubiquitin ligase activity in vitro. Similarities in phenotype, expression, and genetic interactions suggest that mahoganoid and Atrn genes are part of a conserved pathway for regulated protein turnover whose function is essential for neuronal viability.