On Bar Recursive Interpretations of Analysis.

PhDThis dissertation concerns the computational interpretation of analysis via proof interpretations, and examines the variants of bar recursion that have been used to interpret the axiom of choice. It consists of an applied and a theoretical component. The applied part contains a series of case studies which address the issue of understanding the meaning and behaviour of bar recursive programs extracted from proofs in analysis. Taking as a starting point recent work of Escardo and Oliva on the product of selection functions, solutions to Godel's functional interpretation of several well known theorems of mathematics are given, and the semantics of the extracted programs described. In particular, new game-theoretic computational interpretations are found for weak Konig's lemma for 01 -trees and for the minimal-bad-sequence argument. On the theoretical side several new definability results which relate various modes of bar recursion are established. First, a hierarchy of fragments of system T based on finite bar recursion are defined, and it is shown that these fragments are in one-to-one correspondence with the usual fragments based on primitive recursion. Secondly, it is shown that the so called `special' variant of Spector's bar recursion actually defines the general one. Finally, it is proved that modified bar recursion (in the form of the implicitly controlled product of selection functions), open recursion, update recursion and the Berardi-Bezem- Coquand realizer for countable choice are all primitive recursively equivalent in the model of continuous functionals.EPSR

Gwasgariad rhywogaethau dŵr croyw ymledol ym Mhrydain

Mae bioamrywiaeth y byd yn wynebu amryw o fygythiadau o achos gweithgareddau anthropogenig megis dinistrio cynefinoedd, gorddefnyddio adnoddau a llygredd. Yn ogystal, bu cyflwyniad rhywogaethau estron i ecosystemau dieithr yn un o brif achosion colled bioamrywiaeth, gan iddynt gystadlu â rhywogaethau cynhenid am adnoddau, lledu heintiau ac achosi niwed strwythurol. Er hyn, nifer bychan o rywogaethau a gyflwynwyd i ecosystem newydd sy'n llwyddo i ymledu. Rhaid iddynt gael eu cludo a'u cyflwyno, ac yna, sefydlu ac ehangu cyn dod yn rywogaethau ymledol llwyddiannus. Effeithia ymddygiad anifeiliaid ar y broses ymledu, yn enwedig wrth iddynt wasgaru, er mae yna diffyg gwybodaeth ar sut all ffactorau biotig ac anfiotig effeithio ar hyn. Yn yr astudiaeth hon, gan ddefnyddio arenâu arbrofol yn y labordy, astudiwyd ymddygiad dau brif grŵp o anifeiliaid ymledol yn nyfroedd croyw Prydain; cimychiaid yr afon a physgod. Darganfuwyd bod rhywogaethau ymledol o gimychiaid yr afon yn fwy tueddol o wasgaru o'u cymharu â rhai cynhenid (Pennod 3). Dangoswyd hefyd bod cimychiaid yr afon beichiog yr un mor dueddol o wasgaru dros y tir â rhai heb wyau; bu potensial uchel i'r unigolion beichiog gyflwyno eu hepil i gynefin newydd, er bod cimychiaid yr afon ifanc yn cyrraedd trothwy maint cyn iddynt wasgaru dros y tir (Pennod 4). Canfyddir bod parasit ymledol yn lleihau tueddiad cimychiaid yr afon ymledol i wasgaru (Pennod 5). Canlyniad nodedig oedd bod tymheredd yn effeithio'n bositif ar allu pysgod ymledol i nofio, ac felly i wasgaru (Pennod 6), er ni chaiff tymheredd effaith sylweddol ar eu rhyngweithiadau â physgod cynhenid (Pennod 7). Fodd bynnag, amlygir defnyddioldeb arsylwadau uniongyrchol rhyngweithiadau rhyng-rywogaethol, a dangoswyd bod maint y corff yn ffactor bwysig i'w ystyried wrth asesu potensial un rhywogaeth i effeithio'n negyddol ar un arall (Pennod 7). Ar y cyfan, caiff y gwaith hwn oblygiadau penodol (gweler Pennod 8) mewn cadwraeth a rheolaeth rhywogaethau ymledol

Terrestrial dispersal of invasive signal crayfish during vulnerable life stages

1. Aquatic invertebrates commonly disperse between waterbodies by flight, though some decapods can emigrate from the water and walk overland. 2. The signal crayfish (Pacifastacus leniusculus, Dana) is a highly invasive species that can survive for days to weeks out of water, though it is unclear to what extent vulnerable life stages, such as ovigerous females or juvenile crayfish, terrestrially emigrate. Understanding this behaviour is important to consider during the management of crayfish stocks, since a single ovigerous female could potentially introduce hundreds of hatchlings to a new waterbody, which could themselves disperse overland. 3. Here, in a laboratory study, we examined the terrestrial emigration tendency of juvenile crayfish and compared the terrestrial emigration behaviour and overland walking speed of ovigerous and non-ovigerous females. 4. Size had a significant influence on juvenile crayfish terrestrial emigration tendency, where only those larger than 16.6 mm (carapace length) left the water. Ovigerous and non-ovigerous female signal crayfish showed no significant difference in terrestrial emigration tendency nor overland walking speed. 5. This is the first study to directly examine the terrestrial emigration behaviour of crayfish during these different life stages. These findings highlight the importance of considering animal behaviour during management strategies

The impact of streetlights on an aquatic invasive species: artificial light at night alters signal crayfish behaviour

Artificial light at night (ALAN) can significantly alter the behaviour, communication and orientation of animals, and will potentially interact with other stressors to affect biodiversity. Invasive, non-native species are one of the largest threats to freshwater biodiversity; however, the impact of ALAN on such species is unknown. This study assessed the effects of ALAN at ecologically relevant levels on the behaviour of a globally widespread invasive species, the signal crayfish (Pacifastacus leniusculus). In experimental aquaria, crayfish were exposed to periods of daylight, control (<0.1 lx) and street-lit nights to test two hypotheses: (1) signal crayfish under natural conditions are nocturnal animals, spending more time in shelter during the day, whilst active and interacting during the night, and (2) ALAN reduces crayfish activity and intraspecific interactions, whilst increasing their propensity to use shelter. Our results confirm that signal crayfish are largely nocturnal, showing peak activity and interaction levels during control nights, whilst taking refuge during daylight hours. When exposed to short-term simulated light pollution from a streetlight at night however, activity and interactions with conspecifics were significantly reduced compared to control nights, whilst time spent in shelters increased. By altering crayfish behaviour, ALAN may change the ecosystem impacts of invasive crayfish in the wild. This study is the first to show an impact of ALAN on the behaviour of an invasive, non-native species, and provides information for the management of invasive crayfish in areas where ALAN is prevalent

Terrestrial emigration behaviour of two invasive crayfish species

To disperse between isolated waterbodies, freshwater organisms must often cross terrestrial barriers and many freshwater animals that are incapable of flight must rely on transport via flooding events, other animals or anthropogenic activity. Decapods such as crayfish, on the other hand, can disperse to nearby waterbodies by walking on land, a behaviour that has facilitated the spread of invasive species. Overland movement could play a key role in the management of non-native crayfish, though to what extent terrestrial emigration occurs in different species is poorly understood. Here, we directly compared the terrestrial emigration tendency of two non-native crayfish species in Great Britain; red swamp (Procambarus clarkii) and signal (Pacifastacus leniusculus) crayfish. We found that both species emigrated from the water and that there was no significant difference in terms of their terrestrial emigration tendency, suggesting that there is a risk both of these species will migrate overland and disperse to new habitats. This study shows that terrestrial emigration is an important behavioural trait to consider when preventing the escape of crayfish from aquaculture and further spread of invasive species

Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.

BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden

Crayfish plague affects juvenile survival and adult behaviour of invasive signal crayfish

The spread of invasive, non-native species is a key threat to biodiversity. Parasites can play a significant role by influencing their invasive host’s survival or behaviour, which can subsequently alter invasion dynamics. The North American signal crayfish (Pacifastacus leniusculus) is a known carrier of Aphanomyces astaci, an oomycete pathogen that is the causative agent of crayfish plague and fatal to European crayfish species, whereas North American species are considered to be largely resistant. There is some evidence, however, that North American species, can also succumb to crayfish plague, though how A. astaci affects such ‘reservoir hosts’ is rarely considered. Here, we tested the impact of A. astaci infection on signal crayfish, by assessing juvenile survival and adult behaviour following exposure to A. astaci zoospores. Juvenile signal crayfish suffered high mortality 4-weeks post-hatching, but not as older juveniles. Furthermore, adult signal crayfish with high infection levels displayed altered behaviours, being less likely to leave the water, explore terrestrial areas and exhibit escape responses. Overall, we reveal that A. astaci infection affects signal crayfish to a much greater extent than previously considered, which may not only have direct consequences for invasions, but could substantially affect commercially harvested signal crayfish stocks worldwide

Transmission and terrestrial dispersal of non-native ectosymbionts on invasive crayfish

Symbionts are a fundamental component of biological systems, and their survival is highly dependent on transmission and host movement. Ectosymbionts of amphibious animals face the added challenge of having to survive dramatic environmental changes as their hosts cross ecosystem boundaries. Within freshwaters, crayfish are amongst the most widespread invasive species that readily disperse overland and are host to a wide range of ectosymbionts. Relatively little is known about the transmission of these ectosymbionts, including their ability to survive overland host migration. Here, we assessed terrestrial emigration and both inter- and intra-specific transmissions of Xironogiton victoriensis, a non-native branchiobdellidan (Annelida: Clitellata) recently found on invasive signal crayfish (Pacifastacus leniusculus) in the UK. These branchiobdellidans tolerated desiccation and did not alter host terrestrial behaviour. Transmission was rapid between natural signal and novel virile (Orconectes cf. virilis) crayfish hosts, with host interactions facilitating transmission. Thus, branchiobdellidans can disperse via amphibious host behaviour and readily infect novel hosts. These traits facilitate symbionts’ survival and provide access to additional dispersal pathways that are likely to aid transmission