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A number of laser facilities coming online all over the world promise the capability of high-power laser experiments with shot repetition rates between 1 and 10 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: dynamic compression physics, electron transport and isochoric heating, and laser-driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities.
Migratory fishes are natural wonders. For many people, the term migratory fish evokes images of salmon audaciously jumping at waterfalls as they return to their own riverine birthplace to spawn after years of growth in the ocean, but freshwater fishes actually show a broad spectrum of migration strategies. Migratory fishes include small species – three-spined sticklebacks that spawn in coastal streams around the northern Pacific and gobies that move from the ocean into tropical island streams by climbing waterfalls (McDowall, 1988) – as well as some of the largest freshwater fishes in the world, such as the Mekong dog-eating catfish and the Chinese paddlefish (Stone, 2007). Aside from migratory habits, these species have few shared characteristics; they encompass numerous evolutionary lineages, enormous differences in life history, and every possible direction and distance of migration. Biologists treat migratory freshwater fishes as a functional group because their life-history strategy revolves around long-distance movement between ecosystems in a perilous quest to take advantage of both high-quality breeding sites and bountiful feeding areas. As humans have physically blocked fish migrations, degraded breeding and feeding grounds and relentlessly harvested migrants for their flesh and roe, many populations have declined or been extirpated. This chapter will provide an overview of fundamental and applied research that is helping to guide efforts to conserve migratory freshwater fishes.
For practical purposes, we define migratory behaviour as the synchronized movement of a substantial proportion of a population between distinct habitats, which is repeated through time within or across generations. Modern definitions of fish migrations typically recognise both the adaptive benefits of migrating and individual variation in executing the general strategy (see McDowall, 1988; Lucas & Baras, 2001). Not every individual must move, the timing may vary somewhat from year to year, and the motive for migrating may include seeking refuge from harsh conditions in addition to breeding and feeding. Nonetheless, in most cases, migration is critical to individual fitness and population persistence because it enables specialised use of different habitats for growth and reproduction. Where their migration routes are blocked or key habitats are lost, migratory fishes often suffer rapid and catastrophic losses.
Human appropriation and degradation of the Earth's freshwater ecosystems (Vörösmarty et al., 2010; Carpenter et al., 2011) have transformed this reliance on multiple habitats into a detriment for many migratory fishes.
Anterior tongue reduction is indicated when macroglossia causes problems with oral hygiene, airway compromise, deglutition, articulation or orthognathic complications. Causes of macroglossia include hypothyroidism, mucopolysaccharide and lipid storage disease, lymphangioma, haemangioma, neurofibroma, and muscular macroglossia. This paper presents an 11-year experience of anterior tongue reduction at Great Ormond Street Hospital.
Retrospective study of patient medical records identified from the hospital ENT database. Anterior wedge resection was the preferred technique.
Anterior tongue reduction was performed on 18 patients, due to cystic hygroma with tongue involvement (nine patients), Beckwith–Wiedemann syndrome (eight) and Down's syndrome (one). Anterior wedge resection was preferred, using electrocautery in the majority, except for four cases involving CO2 laser. All but one patient had a good surgical outcome (i.e. tongue in mouth at rest). One patient subsequently required multiple laser procedures for recurrent macroglossia.
Anterior tongue reduction can be a safe procedure, with limited post-operative morbidity, consistently resulting in good surgical outcomes and improvement in macroglossia symptoms. Speech development does not appear to be adversely affected.
Multiple surgical procedures have been advocated for the management of problematic drooling in neurologically impaired children. Parotid duct ligation is a quick and simple operation conducted via an intra-oral approach and usually performed simultaneously with other procedures. In this study, we aimed to evaluate the effectiveness of parotid duct ligation as a discrete procedure.
All children who underwent bilateral parotid duct ligation as the solitary operative intervention at that time, between February 2003 and September 2006, were included in the study.
Ten children were studied. Surgery was successful in 80 per cent of cases. One patient (10 per cent) had a post-operative wound infection.
Bilateral parotid duct ligation is an effective yet conservative operation for drooling in neurologically impaired children. It requires minimal surgical dissection and has a low morbidity rate. It should be considered as a potential first-line procedure in children who aspirate, and as a further surgical option in anterior droolers or those who continue to drool unacceptably following prior surgical intervention.
Natural abundances of the stable isotopes, 15N/14N (δ15N) and 13C/12C (δ13C), were used to study temporal host-parasite relationships of the wild rabbit, Oryctolagus cuniculus (L.). During the 12-month sampling period, temporal isotopic shifts in δ15N were noted for dietary vegetation, host rabbit faeces and fur, but not for muscle or stomach contents. δ15N varied temporally for the parasitic cestode species, Mosgovoyia pectinata but not for Cittotaenia denticulata. Similarly, intestinal parasitic nematodes had apparent species-specific δ15N patterns. Only rabbit fur and intestinal parasitic nematodes did not exhibit temporal shifts in δ13C. Overall, host faeces and stomach contents were isotopically indistinct as a likely consequence of coprophagy. Relative to their host, parasitic nematodes were 15N-enriched, consistent with an increase in trophic level status. Conversely, cestodes were 15N-depleted. Isotopically, each parasite reflected a species-specific relationship with their rabbit host. This technique could be utilized to integrate parasites into food-web studies.
The US Naval Research Laboratory (NRL) is developing technologies that will enable Navy-relevant missions with the smallest practical Micro Air Vehicles (MAVs). The NRL Micro Tactical Expendable (MITE) air vehicle is a result of this research. MITE is a hand-launched, dual-propeller, fixed-wing air vehicle, with a 25cm chord and a wingspan of 25–47cm, depending on payload weight. Vehicle gross weight is 130–350g. Miniature autopilot systems, based on visual imaging techniques, are being developed for MITE. These will be used in conjunction with conventional autopilot sensors to allow the MITE to fly autonomously. This paper provides an overview of the MITE development, including aerodynamic design considerations, electric propulsion, and vision-based autopilot research. Also presented is a rationale for the development of control laws that can direct the behavior of large groups of MAVs or other vehicle agents. Dubbed ‘physicomimetics,’ this process can bring about the self-assembly of complex MAV formations, though individual MAVs have minimal onboard processing power and limited local sensing capabilities.
The recovery of nitrogen ‘retained’ through cover crop
uptake, delayed ploughing and
immobilization by straw was assessed in a spring cropping rotation on a
chalk loam in Eastern
England (1989–96). The effect of annual cover cropping on yield of
the subsequent spring crops and
on the soil N balance was also investigated. The recovery of retained N
was in part dependent upon
cover crop management. Late August-sown cover crops which were incorporated
tended to reduce spring crop yields and crop N offtake. Adverse effects
on soil N supply, seedbed
conditions and soil water reserves were not in evidence and so an allelopathic
effect from the
decomposition of the rye cover crop, previously reported by others, may
be responsible for the
reduction in yield of spring crops. When the cover crops were drilled later
and their early destruction
was followed by a short fallow period, spring crop yields and N offtake
were increased. The soil N
balance indicated that over the course of the experiment there was a positive
N input to the system
due to continuous cover cropping. This input may be held as immobilized
organic N, in which case
it could be made available to subsequent crops over a number of years or
lost via other routes. Nitrate
concentrations in drainage water increased with the number of years under
A review of the relationship between elastic moduli and interatomic force constants precedes the description of a method for determining the composition dependence of single crystal elastic moduli of disordered alloys having the face-centered cubic structure. The method treats the alloy as a virtual crystal, characterized by an effective pair potential between atoms. Results of calculations are presented using experimental data on Cu-rich Cu-Al alloys.
In , Wong defined a quasi-permutation group of degree n to be a finite group G of automorphisms of an n-dimensional complex vector space such that every element of G has non-negative integral trace. The terminology derives from the fact that if G is a finite group of permutations of a set ω of size n, and we think of G as acting on the complex vector space with basis ω, then the trace of an element g ∈ G is equal to the number of points of ω fixed by g. In  and , Wong studied the extent to which some facts about permutation groups generalize to the quasi-permutation group situation. Here we investigate further the analogy between permutation groups and quasipermutation groups by studying the relation between the minimal degree of a faithful permutation representation of a given finite group G and the minimal degree of a faithful quasi-permutation representation. We shall often prefer to work over the rational field rather than the complex field.
The purpose of this paper is to reconsider the significance of the so-called ‘Late Celtic rubbish heap’ near Oare (Nat. Grid Ref. SU 172643) in the parish of Wilcot, near Marlborough in central Wiltshire and to assess its implications for Savernake ware, a regional variety of grey culinary coarse pottery, known to have been produced in Savernake Forest, just south of Marlborough, Wiltshire. The site in question (FIG. I), 6–4 km south-west of the Roman walled town of Cunetio (Mildenhall) was dug into in 1907–8 by Benjamin and Maud Cunnington. Mr. and Mrs. Cunnington were attached to Devizes Museum from the late nineteenth until almost the mid twentieth century and became well known for their many excavations and publications, particularly on prehistoric sites in Wiltshire.
The site was first occupied in the Bronze Age by a small agricultural settlement, consisting of two circular timber houses with ancillary structures and ditches. One house was eventually replaced by a stone structure. A single radiocarbon determination suggests that the settlement is to be dated within the period 1700–1300 B.C. The Iron Age settlement of Trevisker Round was probably established in the second century B.C., if not earlier. An original inner enclosure, half an acre in area, housing a single defended farmstead, was later superseded by a larger defended enclosure, 3 acres in area, also with circular timber houses and occupation areas. This occupation was followed at the end of the first century A.D., by a Romano-British phase of occupation, which lasted until the middle of the second century.
Of the problems facing historians of Roman Britain few are so pressing, or so difficult to solve, as those associated with the Roman occupations of Scotland. The difficulties stem from the sparsity of contemporary or near-contemporary literary accounts, but they are exacerbated by the apparent lack of dated building inscriptions firmly assignable to the second Antonine period. Nevertheless, any assessment of Antonine Scotland must clearly start from the ancient historians, take into account all the available inscriptions and add the evidence provided by coins. The structural evidence for the forts has to be reviewed against this background. However, in recent years we have come to realise more and more that all these categories of evidence taken together are not enough to allow precise conclusions on some vital points. All this applies primarily to the Antonine period: the Flavian occupation indeed has its problems, but on the whole they are relatively minor ones, and do not involve widely different chronological interpretations.
We prove here that the (saturated) formation generated by a finite soluble group has only finitely many (saturated) subformations. This answers a question asked by Professor W. Gaschütz. Some partial results are also given in the case of a formation generated by an arbitrary finite group.