Nucleobases are nitrogenous bases composed of monomers that are a major constituent of RNA and DNA, which are an essential part of any cellular life on the Earth. The search for nucleobases in the interstellar medium remains a major challenge, however, the recent detection of nucleobases in meteorite samples and laboratory synthesis in simulated analogue experiments have confirmed their abiotic origin and a possible route for their delivery to the Earth. Nevertheless, cellular life is based on the interacting network of complex structures, and there is substantial lack of information on the possible routes by which such ordered structures may be formed in the prebiotic environment. In the current study, we present the evidence for the synthesis of complex structures due to shock processing of nucleobases. The nucleobases were subjected to the reflected shock temperature of 3500–7000 K (estimated) and pressure of about 15–34 bar for over ~2 ms timescale. Under such extreme thermodynamic conditions, the nucleobases sample experiences superheating and subsequent cooling. Electron microscopic studies of shock processed residue show that nucleobases result in spontaneous formation of complex structures when subjected to extreme conditions of shock. These results suggest that impact shock processes might have contributed to the self-assembly of biologically relevant structures and the origin of life.

Solar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful flares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like stars. In this study, we investigate the possibility of using coronal dimming as a proxy to diagnose stellar CMEs. By simulating a realistic solar CME event and corresponding coronal dimming using a global magnetohydrodynamics model (AWSoM: Alfvén-wave Solar Model), we first demonstrate the capability of the model to reproduce solar observations. We then extend the model for simulating stellar CMEs by modifying the input magnetic flux density as well as the initial magnetic energy of the CME flux rope. Our result suggests that with improved instrument sensitivity, it is possible to detect the coronal dimming signals induced by the stellar CMEs.

In support of the disposal system safety case for a geological disposal facility (GDF) there is a requirement to consider 'what-if' hypothetical scenarios for post-closure nuclear criticality. Although all such scenarios are considered very unlikely, one 'what-if' scenario is the mobilization of fissile material from a number of waste packages and its slow accumulation within the GDF or the immediate surroundings. Should sufficient fissile material accumulate a quasi-steady-state (QSS) transient criticality event could result. A computer model has been developed to understand the evolution and consequences of such an event.

Since a postulated QSS criticality could persist for many millennia, building confidence in the modelling approach is difficult. However, the Oklo natural reactors in Africa operated for similar durations around two billion years ago, providing a natural analogue for comparison. This paper describes the modelling approach, its application to hypothetical criticality events for a GDF, and how the model can be compared to Oklo. The model results are found to be in agreement with the observational evidence from Oklo, building confidence in the use of the QSS model to simulate postulated post-closure criticality events in GDFs.

In support of the Radioactive Waste Management (RWM) safety case for a geological disposal facility (GDF) in the UK, there is a regulatory requirement to consider the likelihood and consequences of nuclear criticality. Waste packages are designed to ensure that criticality is not possible during the transport and operational phases of a GDF and for a significant period post-closure. However, over longer post-closure timescales, conditions in the GDF will evolve.

For waste packages containing spent fuel, it can be shown that, under certain conditions, package flooding could result in a type of criticality event referred to as 'quasi-steady-state' (QSS). Although unlikely, this defines a 'what-if' scenario for understanding the potential consequences of post-closure criticality. This paper provides an overview of a methodology to understand QSS criticality and its application to a spent fuel waste package.

The power of such a hypothetical criticality event is typically estimated to be a few kilowatts: comparable with international studies of similar systems and the decay heat for which waste packages are designed. This work has built confidence in the methodology and supports RWM's demonstration that post-closure criticality is not a significant concern.

A geological disposal facility (GDF) will include fissile materials that could, under certain conditions, lead to criticality. Demonstration of criticality safety therefore forms an important part of a GDF's safety case.

Containment provided by the waste package will contribute to criticality safety during package transport and the GDF operational phase. The GDF multiple-barrier system will ensure that criticality is prevented for some time after facility closure. However, on longer post-closure timescales, conditions in the GDF will evolve and it is necessary to demonstrate: an understanding of the conditions under which criticality could occur; the likelihood of such conditions occurring; and the consequences of criticality should it occur.

Work has addressed disposal of all of the UK's higher-activity wastes in three illustrative geologies. This paper, however, focuses on presenting results to support safe disposal of spent fuel, plutonium and highlyenriched uranium in higher-strength rock.

The results support a safety case assertion that post-closure criticality is of low likelihood and, if it was to occur, the consequences would be tolerable.

Neighboring tidewater glaciers often exhibit asynchronous dynamic behavior, despite relatively uniform regional atmospheric and oceanic forcings. This variability may be controlled by a combination of local factors, including glacier and fjord geometry, fjord heat content and circulation, and glacier surface melt. In order to characterize and understand contrasts in adjacent tidewater glacier and fjord dynamics, we made coincident ice-ocean-atmosphere observations at high temporal resolution (minutes to weeks) within a 10 000 km2 area near Uummannaq, Greenland. Water column velocity, temperature and salinity measurements reveal systematic differences in neighboring fjords that imply contrasting circulation patterns. The observed ocean velocity and hydrography, combined with numerical modeling, suggest that subglacial discharge plays a major role in setting fjord conditions. In addition, satellite remote sensing of seasonal ice flow speed and terminus position reveal both speedup and slow-down in response to melt, as well as differences in calving style among the neighboring glaciers. Glacier force budgets and modeling also point toward subglacial discharge as a key factor in glacier behavior. For the studied region, individual glacier and fjord geometry modulate subglacial discharge, which leads to contrasts in both fjord and glacier dynamics.

In wild rabbits (Oryctolagus cuniculus) on an estate in Perthshire, central Scotland, the seroprevalence of Toxoplasma gondii was 18/548 (3·3%). The wild rabbit could be a T. gondii reservoir and it has potential value as a sentinel of T. gondii in environmental substrates. Toxoplasma gondii was associated with female sex (P < 0·001) and with relatively heavy infections by Eimeria stiedae (P = 0·036). It was not associated with the intensity of coccidial oocysts, the severity of myxomatosis caused by the virus Myxomatosis cuniculi, the intensity of roundworm eggs, the year or season, rabbit age or distance from farm buildings. Coinfections could have been affected by gestational down regulation of type 1 T helper cells. A sudden influx or release of T. gondii oocysts might have occurred. This is the first report of T. gondii in any wild herbivore in Scotland and also the first report of lapine T. gondii as a coinfection with E. stiedae, M. cuniculi and helminths.

An overview of the Czech national R&D project HiLASE (High average power pulsed laser) is presented. The project focuses on the development of advanced high repetition rate, diode pumped solid state laser (DPSSL) systems with energies in the range from mJ to 100 J and repetition rates in the range from 10 Hz to 100 kHz. Some applications of these lasers in research and hi-tech industry are also presented.

Field collections of over-wintering and summer adults and nymphs of Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), Lygus borealis (Kelton), and Lygus elisus Van Duzee were made weekly in five fields in Saskatchewan in 1998 and 1999. The crops sampled were alfalfa, Medicago sativa L. (Leguminosae), canola, Brassica napus L. (Cruciferae), and mustard, Sinapis alba L. (Cruciferae), at Vonda, and alfalfa and canola at Saskatoon. In alfalfa, the most abundant Lygus spp. found in May and June were over-wintering adult L. lineolaris and (or) L. borealis; the predominant species in mid-June to early July was L. borealis; and the population from mid-July to late August was dominated by L. lineolaris. In canola, adult populations of Lygus spp. were not found until mid-June. The predominant species, L. lineolaris, probably over-wintering adults, was first detected in canola at the early bud stage in late June to early July; high numbers of L. lineolaris adults occurred in canola in mid-August. Populations of Lygus spp. in organic mustard were negligible. Dissections of field-collected Lygus spp. nymphs revealed parasitism in up to 70% of the midsummer population in alfalfa. In contrast, less than 1% of the late-season Lygus spp. population, primarily L. lineolaris in canola and L. lineolaris and L. borealis in alfalfa, was parasitized.

Plant bugs in the genus Lygus (Hahn) (Hemiptera: Miridae) are sporadic pests of canola, Brassica napus L. (Brassicaceae) and Brassica rapa L., in western Canada and infestations appear to have become increasingly common and severe in recent years. Surveys conducted from 1998 to 2000 identified a "northern" assemblage in the boreal ecoregion that was dominated by Lygus lineolaris (Palisot de Beauvois), with minor representation of Lygus borealis (Kelton), Lygus elisus (Van Duzee), and Lygus keltoni (Schwartz). A "southern" assemblage in the grassland ecoregions was dominated by L. keltoni, with a substantial abundance of L. elisus and L. borealis and with few L. lineolaris in the driest areas. The assemblage from the parkland ecoregion was variable but with few L. elisus. The boreal plains and parkland ecoregions of Alberta had the most serious and persistent infestations of Lygus spp. Relative species composition of the Lygus assemblage at the bolting stage was not related to the overall abundance of these bugs at the early pod stage. Lygus species assemblages were similar in terms of composition and relative abundance at the bolting and early pod stages of canola. A shift in species proportions in favour of L. lineolaris in the north and L. keltoni in the south and a decrease of L. elisus has taken place relative to studies conducted in the 1980's.

Leek moth, Acrolepiopsis assectella, recently became established in the Ottawa Valley, where it significantly damages garlic, leek, and onion (Allium L., Liliaceae) crops. At a threshold of 7 °C, populations in eastern Ontario require 444.6 day-degrees to develop from egg to adult. Pheromone-trap data identify spring, early-summer, and late-summer flight periods of overwintered 1st- and 2nd-generation adults, respectively. Depending on ambient temperatures, the life cycle takes 3–6 weeks in the field, with three generations possible. Management strategies such as application of reduced-risk foliar insecticides and use of row covers require precise timing to target appropriate life-cycle stages. Implementation windows can be determined by incorporating pheromone-trap data and ambient air temperature into a life-cycle development model. A proposed integrated pest management program will involve the use of pesticides, mechanical barriers, and classical biological control.